diff --git a/Cargo.toml b/Cargo.toml
index b8f32a58..17999251 100644
--- a/Cargo.toml
+++ b/Cargo.toml
@@ -31,6 +31,9 @@ rand = "0.8"
 nonempty = "0.6"
 subtle = "2.3"
 
+# Developer tooling dependencies
+plotters = { version = "0.3.0", optional = true }
+
 [dependencies.halo2]
 git = "https://github.com/zcash/halo2.git"
 rev = "0448584333c1e262e4a7dbaefa6fdd896bdaaefb"
@@ -52,6 +55,7 @@ proptest = "1.0.0"
 bench = false
 
 [features]
+dev-graph = ["halo2/dev-graph", "plotters"]
 test-dependencies = ["proptest"]
 
 [[bench]]
diff --git a/src/circuit/gadget/poseidon.rs b/src/circuit/gadget/poseidon.rs
index 1ebb35b0..3ea50a74 100644
--- a/src/circuit/gadget/poseidon.rs
+++ b/src/circuit/gadget/poseidon.rs
@@ -8,6 +8,9 @@ use halo2::{
     plonk::Error,
 };
 
+mod pow5t3;
+pub use pow5t3::{Pow5T3Chip, Pow5T3Config};
+
 /// The set of circuit instructions required to use the [`Poseidon`] gadget.
 pub trait PoseidonInstructions<F: FieldExt>: Chip<F> {
     /// Variable representing the state over which the Poseidon permutation operates.
diff --git a/src/circuit/gadget/poseidon/pow5t3.rs b/src/circuit/gadget/poseidon/pow5t3.rs
new file mode 100644
index 00000000..026c570a
--- /dev/null
+++ b/src/circuit/gadget/poseidon/pow5t3.rs
@@ -0,0 +1,570 @@
+use halo2::{
+    arithmetic::FieldExt,
+    circuit::{Cell, Chip, Layouter, Region},
+    plonk::{Advice, Column, ConstraintSystem, Error, Expression, Fixed, Permutation, Selector},
+    poly::Rotation,
+};
+
+use super::PoseidonInstructions;
+use crate::primitives::poseidon::{Mds, Spec};
+
+const WIDTH: usize = 3;
+
+/// Configuration for an [`Pow5T3Chip`].
+#[derive(Clone, Debug)]
+pub struct Pow5T3Config<F: FieldExt> {
+    state: [Column<Advice>; WIDTH],
+    state_permutation: Permutation,
+    partial_sbox: Column<Advice>,
+    rc_a: [Column<Fixed>; WIDTH],
+    rc_b: [Column<Fixed>; WIDTH],
+    s_full: Selector,
+    s_partial: Selector,
+    s_final: Selector,
+
+    half_full_rounds: usize,
+    half_partial_rounds: usize,
+    alpha: [u64; 4],
+    round_constants: Vec<[F; WIDTH]>,
+    m_reg: Mds<F, WIDTH>,
+    m_inv: Mds<F, WIDTH>,
+}
+
+/// A Poseidon chip using an $x^5$ S-Box, with a width of 3, suitable for a 2:1 reduction.
+#[derive(Debug)]
+pub struct Pow5T3Chip<F: FieldExt> {
+    config: Pow5T3Config<F>,
+}
+
+impl<F: FieldExt> Pow5T3Chip<F> {
+    /// Configures this chip for use in a circuit.
+    //
+    // TODO: Does the rate need to be hard-coded here, or only the width? It probably
+    // needs to be known wherever we implement the hashing gadget, but it isn't strictly
+    // necessary for the permutation.
+    pub fn configure<S: Spec<F, WIDTH, 2>>(
+        meta: &mut ConstraintSystem<F>,
+        spec: S,
+        state: [Column<Advice>; WIDTH],
+    ) -> Pow5T3Config<F> {
+        // Generate constants for the Poseidon permutation.
+        // This gadget requires R_F and R_P to be even.
+        assert!(S::full_rounds() & 1 == 0);
+        assert!(S::partial_rounds() & 1 == 0);
+        let half_full_rounds = S::full_rounds() / 2;
+        let half_partial_rounds = S::partial_rounds() / 2;
+        let (round_constants, m_reg, m_inv) = spec.constants();
+
+        let state_permutation =
+            Permutation::new(meta, &[state[0].into(), state[1].into(), state[2].into()]);
+
+        let partial_sbox = meta.advice_column();
+
+        let rc_a = [
+            meta.fixed_column(),
+            meta.fixed_column(),
+            meta.fixed_column(),
+        ];
+        let rc_b = [
+            meta.fixed_column(),
+            meta.fixed_column(),
+            meta.fixed_column(),
+        ];
+
+        let s_full = meta.selector();
+        let s_partial = meta.selector();
+        let s_final = meta.selector();
+
+        let alpha = [5, 0, 0, 0];
+        let pow_5 = |v: Expression<F>| {
+            let v2 = v.clone() * v.clone();
+            v2.clone() * v2 * v
+        };
+
+        meta.create_gate("full round", |meta| {
+            let cur_0 = meta.query_advice(state[0], Rotation::cur());
+            let cur_1 = meta.query_advice(state[1], Rotation::cur());
+            let cur_2 = meta.query_advice(state[2], Rotation::cur());
+            let next = [
+                meta.query_advice(state[0], Rotation::next()),
+                meta.query_advice(state[1], Rotation::next()),
+                meta.query_advice(state[2], Rotation::next()),
+            ];
+
+            let rc_0 = meta.query_fixed(rc_a[0], Rotation::cur());
+            let rc_1 = meta.query_fixed(rc_a[1], Rotation::cur());
+            let rc_2 = meta.query_fixed(rc_a[2], Rotation::cur());
+
+            let s_full = meta.query_selector(s_full, Rotation::cur());
+
+            let full_round = |next_idx: usize| {
+                s_full.clone()
+                    * (pow_5(cur_0.clone() + rc_0.clone()) * m_reg[next_idx][0]
+                        + pow_5(cur_1.clone() + rc_1.clone()) * m_reg[next_idx][1]
+                        + pow_5(cur_2.clone() + rc_2.clone()) * m_reg[next_idx][2]
+                        - next[next_idx].clone())
+            };
+
+            vec![full_round(0), full_round(1), full_round(2)]
+        });
+
+        meta.create_gate("partial round", |meta| {
+            let cur_0 = meta.query_advice(state[0], Rotation::cur());
+            let cur_1 = meta.query_advice(state[1], Rotation::cur());
+            let cur_2 = meta.query_advice(state[2], Rotation::cur());
+            let mid_0 = meta.query_advice(partial_sbox, Rotation::cur());
+            let next_0 = meta.query_advice(state[0], Rotation::next());
+            let next_1 = meta.query_advice(state[1], Rotation::next());
+            let next_2 = meta.query_advice(state[2], Rotation::next());
+
+            let rc_a0 = meta.query_fixed(rc_a[0], Rotation::cur());
+            let rc_a1 = meta.query_fixed(rc_a[1], Rotation::cur());
+            let rc_a2 = meta.query_fixed(rc_a[2], Rotation::cur());
+            let rc_b0 = meta.query_fixed(rc_b[0], Rotation::cur());
+            let rc_b1 = meta.query_fixed(rc_b[1], Rotation::cur());
+            let rc_b2 = meta.query_fixed(rc_b[2], Rotation::cur());
+
+            let s_partial = meta.query_selector(s_partial, Rotation::cur());
+
+            let partial_round_linear = |idx: usize, rc_b: Expression<F>| {
+                s_partial.clone()
+                    * (mid_0.clone() * m_reg[idx][0]
+                        + (cur_1.clone() + rc_a1.clone()) * m_reg[idx][1]
+                        + (cur_2.clone() + rc_a2.clone()) * m_reg[idx][2]
+                        + rc_b
+                        - (next_0.clone() * m_inv[idx][0]
+                            + next_1.clone() * m_inv[idx][1]
+                            + next_2.clone() * m_inv[idx][2]))
+            };
+
+            vec![
+                s_partial.clone() * (pow_5(cur_0 + rc_a0) - mid_0.clone()),
+                s_partial.clone()
+                    * (pow_5(
+                        mid_0.clone() * m_reg[0][0]
+                            + (cur_1.clone() + rc_a1.clone()) * m_reg[0][1]
+                            + (cur_2.clone() + rc_a2.clone()) * m_reg[0][2]
+                            + rc_b0,
+                    ) - (next_0.clone() * m_inv[0][0]
+                        + next_1.clone() * m_inv[0][1]
+                        + next_2.clone() * m_inv[0][2])),
+                partial_round_linear(1, rc_b1),
+                partial_round_linear(2, rc_b2),
+            ]
+        });
+
+        meta.create_gate("final full round", |meta| {
+            let cur = [
+                meta.query_advice(state[0], Rotation::cur()),
+                meta.query_advice(state[1], Rotation::cur()),
+                meta.query_advice(state[2], Rotation::cur()),
+            ];
+            let next = [
+                meta.query_advice(state[0], Rotation::next()),
+                meta.query_advice(state[1], Rotation::next()),
+                meta.query_advice(state[2], Rotation::next()),
+            ];
+            let rc = [
+                meta.query_fixed(rc_a[0], Rotation::cur()),
+                meta.query_fixed(rc_a[1], Rotation::cur()),
+                meta.query_fixed(rc_a[2], Rotation::cur()),
+            ];
+            let s_final = meta.query_selector(s_final, Rotation::cur());
+
+            let final_full_round = |idx: usize| {
+                s_final.clone() * (pow_5(cur[idx].clone() + rc[idx].clone()) - next[idx].clone())
+            };
+            vec![
+                final_full_round(0),
+                final_full_round(1),
+                final_full_round(2),
+            ]
+        });
+
+        Pow5T3Config {
+            state,
+            state_permutation,
+            partial_sbox,
+            rc_a,
+            rc_b,
+            s_full,
+            s_partial,
+            s_final,
+            half_full_rounds,
+            half_partial_rounds,
+            alpha,
+            round_constants,
+            m_reg,
+            m_inv,
+        }
+    }
+
+    fn construct(config: Pow5T3Config<F>) -> Self {
+        Pow5T3Chip { config }
+    }
+}
+
+impl<F: FieldExt> Chip<F> for Pow5T3Chip<F> {
+    type Config = Pow5T3Config<F>;
+    type Loaded = ();
+
+    fn config(&self) -> &Self::Config {
+        &self.config
+    }
+
+    fn loaded(&self) -> &Self::Loaded {
+        &()
+    }
+}
+
+impl<F: FieldExt> PoseidonInstructions<F> for Pow5T3Chip<F> {
+    type State = Pow5T3State<F>;
+
+    fn permute(
+        &self,
+        layouter: &mut impl Layouter<F>,
+        initial_state: &Self::State,
+    ) -> Result<Self::State, Error> {
+        let config = self.config();
+
+        layouter.assign_region(
+            || "permute state",
+            |mut region| {
+                // Load the initial state into this region.
+                let state = Pow5T3State::load(&mut region, &config, initial_state)?;
+
+                let state = (0..config.half_full_rounds).fold(Ok(state), |res, r| {
+                    res.and_then(|state| state.full_round(&mut region, &config, r, r))
+                })?;
+
+                let state = (0..config.half_partial_rounds).fold(Ok(state), |res, r| {
+                    res.and_then(|state| {
+                        state.partial_round(
+                            &mut region,
+                            &config,
+                            config.half_full_rounds + 2 * r,
+                            config.half_full_rounds + r,
+                        )
+                    })
+                })?;
+
+                (0..config.half_full_rounds).fold(Ok(state), |res, r| {
+                    res.and_then(|state| {
+                        if r < config.half_full_rounds - 1 {
+                            state.full_round(
+                                &mut region,
+                                &config,
+                                config.half_full_rounds + 2 * config.half_partial_rounds + r,
+                                config.half_full_rounds + config.half_partial_rounds + r,
+                            )
+                        } else {
+                            state.final_round(
+                                &mut region,
+                                &config,
+                                config.half_full_rounds + 2 * config.half_partial_rounds + r,
+                                config.half_full_rounds + config.half_partial_rounds + r,
+                            )
+                        }
+                    })
+                })
+            },
+        )
+    }
+}
+
+#[derive(Debug)]
+struct StateWord<F: FieldExt> {
+    var: Cell,
+    value: Option<F>,
+}
+
+#[derive(Debug)]
+pub struct Pow5T3State<F: FieldExt>([StateWord<F>; WIDTH]);
+
+impl<F: FieldExt> Pow5T3State<F> {
+    fn full_round(
+        self,
+        region: &mut Region<F>,
+        config: &Pow5T3Config<F>,
+        round: usize,
+        offset: usize,
+    ) -> Result<Self, Error> {
+        Self::round(region, config, round, offset, config.s_full, |_| {
+            let q_0 = self.0[0]
+                .value
+                .map(|v| v + config.round_constants[round][0]);
+            let q_1 = self.0[1]
+                .value
+                .map(|v| v + config.round_constants[round][1]);
+            let q_2 = self.0[2]
+                .value
+                .map(|v| v + config.round_constants[round][2]);
+
+            let r_0 = q_0.map(|v| v.pow(&config.alpha));
+            let r_1 = q_1.map(|v| v.pow(&config.alpha));
+            let r_2 = q_2.map(|v| v.pow(&config.alpha));
+
+            let m = &config.m_reg;
+            let r = r_0.and_then(|r_0| r_1.and_then(|r_1| r_2.map(|r_2| [r_0, r_1, r_2])));
+
+            Ok((
+                round + 1,
+                [
+                    r.map(|r| m[0][0] * r[0] + m[0][1] * r[1] + m[0][2] * r[2]),
+                    r.map(|r| m[1][0] * r[0] + m[1][1] * r[1] + m[1][2] * r[2]),
+                    r.map(|r| m[2][0] * r[0] + m[2][1] * r[1] + m[2][2] * r[2]),
+                ],
+            ))
+        })
+    }
+
+    fn partial_round(
+        self,
+        region: &mut Region<F>,
+        config: &Pow5T3Config<F>,
+        round: usize,
+        offset: usize,
+    ) -> Result<Self, Error> {
+        Self::round(region, config, round, offset, config.s_partial, |region| {
+            let m = &config.m_reg;
+
+            let p = self.0[0].value.and_then(|p_0| {
+                self.0[1]
+                    .value
+                    .and_then(|p_1| self.0[2].value.map(|p_2| [p_0, p_1, p_2]))
+            });
+
+            let r = p.map(|p| {
+                [
+                    (p[0] + config.round_constants[round][0]).pow(&config.alpha),
+                    p[1] + config.round_constants[round][1],
+                    p[2] + config.round_constants[round][2],
+                ]
+            });
+
+            region.assign_advice(
+                || format!("round_{} partial_sbox", round),
+                config.partial_sbox,
+                offset,
+                || r.map(|r| r[0]).ok_or(Error::SynthesisError),
+            )?;
+
+            let p_mid = r.map(|r| {
+                [
+                    m[0][0] * r[0] + m[0][1] * r[1] + m[0][2] * r[2],
+                    m[1][0] * r[0] + m[1][1] * r[1] + m[1][2] * r[2],
+                    m[2][0] * r[0] + m[2][1] * r[1] + m[2][2] * r[2],
+                ]
+            });
+
+            // Load the second round constants.
+            let mut load_round_constant = |i: usize| {
+                region.assign_fixed(
+                    || format!("round_{} rc_{}", round + 1, i),
+                    config.rc_b[i],
+                    offset,
+                    || Ok(config.round_constants[round + 1][i]),
+                )
+            };
+            for i in 0..WIDTH {
+                load_round_constant(i)?;
+            }
+
+            let r_mid = p_mid.map(|p| {
+                [
+                    (p[0] + config.round_constants[round + 1][0]).pow(&config.alpha),
+                    p[1] + config.round_constants[round + 1][1],
+                    p[2] + config.round_constants[round + 1][2],
+                ]
+            });
+
+            Ok((
+                round + 2,
+                [
+                    r_mid.map(|r| m[0][0] * r[0] + m[0][1] * r[1] + m[0][2] * r[2]),
+                    r_mid.map(|r| m[1][0] * r[0] + m[1][1] * r[1] + m[1][2] * r[2]),
+                    r_mid.map(|r| m[2][0] * r[0] + m[2][1] * r[1] + m[2][2] * r[2]),
+                ],
+            ))
+        })
+    }
+
+    fn final_round(
+        self,
+        region: &mut Region<F>,
+        config: &Pow5T3Config<F>,
+        round: usize,
+        offset: usize,
+    ) -> Result<Self, Error> {
+        Self::round(region, config, round, offset, config.s_final, |_| {
+            let mut new_state = self
+                .0
+                .iter()
+                .zip(config.round_constants[round].iter())
+                .map(|(word, rc)| word.value.map(|v| (v + rc).pow(&config.alpha)));
+
+            Ok((
+                round + 1,
+                [
+                    new_state.next().unwrap(),
+                    new_state.next().unwrap(),
+                    new_state.next().unwrap(),
+                ],
+            ))
+        })
+    }
+
+    fn load(
+        region: &mut Region<F>,
+        config: &Pow5T3Config<F>,
+        initial_state: &Self,
+    ) -> Result<Self, Error> {
+        let mut load_state_word = |i: usize| {
+            let value = initial_state.0[i].value;
+            let var = region.assign_advice(
+                || format!("load state_{}", i),
+                config.state[i],
+                0,
+                || value.ok_or(Error::SynthesisError),
+            )?;
+            region.constrain_equal(&config.state_permutation, initial_state.0[i].var, var)?;
+            Ok(StateWord { var, value })
+        };
+
+        Ok(Pow5T3State([
+            load_state_word(0)?,
+            load_state_word(1)?,
+            load_state_word(2)?,
+        ]))
+    }
+
+    fn round(
+        region: &mut Region<F>,
+        config: &Pow5T3Config<F>,
+        round: usize,
+        offset: usize,
+        round_gate: Selector,
+        round_fn: impl FnOnce(&mut Region<F>) -> Result<(usize, [Option<F>; WIDTH]), Error>,
+    ) -> Result<Self, Error> {
+        // Enable the required gate.
+        round_gate.enable(region, offset)?;
+
+        // Load the round constants.
+        let mut load_round_constant = |i: usize| {
+            region.assign_fixed(
+                || format!("round_{} rc_{}", round, i),
+                config.rc_a[i],
+                offset,
+                || Ok(config.round_constants[round][i]),
+            )
+        };
+        for i in 0..WIDTH {
+            load_round_constant(i)?;
+        }
+
+        // Compute the next round's state.
+        let (next_round, next_state) = round_fn(region)?;
+
+        let mut next_state_word = |i: usize| {
+            let value = next_state[i];
+            let var = region.assign_advice(
+                || format!("round_{} state_{}", next_round, i),
+                config.state[i],
+                offset + 1,
+                || value.ok_or(Error::SynthesisError),
+            )?;
+            Ok(StateWord { var, value })
+        };
+
+        Ok(Pow5T3State([
+            next_state_word(0)?,
+            next_state_word(1)?,
+            next_state_word(2)?,
+        ]))
+    }
+}
+
+#[cfg(test)]
+mod tests {
+    use halo2::{
+        circuit::{layouter, Layouter},
+        dev::MockProver,
+        pasta::Fp,
+        plonk::{Assignment, Circuit, ConstraintSystem, Error},
+    };
+
+    use super::{PoseidonInstructions, Pow5T3Chip, Pow5T3Config, Pow5T3State, StateWord};
+    use crate::primitives::poseidon::OrchardNullifier;
+
+    struct MyCircuit {}
+
+    impl Circuit<Fp> for MyCircuit {
+        type Config = Pow5T3Config<Fp>;
+
+        fn configure(meta: &mut ConstraintSystem<Fp>) -> Pow5T3Config<Fp> {
+            let state = [
+                meta.advice_column(),
+                meta.advice_column(),
+                meta.advice_column(),
+            ];
+
+            Pow5T3Chip::configure(meta, OrchardNullifier, state)
+        }
+
+        fn synthesize(
+            &self,
+            cs: &mut impl Assignment<Fp>,
+            config: Pow5T3Config<Fp>,
+        ) -> Result<(), Error> {
+            let mut layouter = layouter::SingleChipLayouter::new(cs)?;
+
+            let initial_state = layouter.assign_region(
+                || "prepare initial state",
+                |mut region| {
+                    let mut state_word = |i: usize| {
+                        let value = Some(Fp::from(i as u64));
+                        let var = region.assign_advice(
+                            || format!("load state_{}", i),
+                            config.state[i],
+                            0,
+                            || value.ok_or(Error::SynthesisError),
+                        )?;
+                        Ok(StateWord { var, value })
+                    };
+
+                    Ok(Pow5T3State([
+                        state_word(0)?,
+                        state_word(1)?,
+                        state_word(2)?,
+                    ]))
+                },
+            )?;
+
+            let chip = Pow5T3Chip::construct(config);
+            chip.permute(&mut layouter, &initial_state).map(|_| ())
+        }
+    }
+
+    #[test]
+    fn poseidon() {
+        let k = 6;
+        let circuit = MyCircuit {};
+        let prover = MockProver::run(k, &circuit, vec![]).unwrap();
+        assert_eq!(prover.verify(), Ok(()))
+    }
+
+    #[cfg(feature = "dev-graph")]
+    #[test]
+    fn print_poseidon_chip() {
+        use plotters::prelude::*;
+
+        let root = BitMapBackend::new("poseidon-chip-layout.png", (1024, 768)).into_drawing_area();
+        root.fill(&WHITE).unwrap();
+        let root = root
+            .titled("Poseidon Chip Layout", ("sans-serif", 60))
+            .unwrap();
+
+        let circuit = MyCircuit {};
+        halo2::dev::circuit_layout(&circuit, &root).unwrap();
+    }
+}
diff --git a/src/primitives/poseidon.rs b/src/primitives/poseidon.rs
index e1954545..426fd939 100644
--- a/src/primitives/poseidon.rs
+++ b/src/primitives/poseidon.rs
@@ -68,7 +68,7 @@ pub trait Spec<F: FieldExt, const T: usize, const RATE: usize> {
 }
 
 /// Runs the Poseidon permutation on the given state.
-fn permute<F: FieldExt, S: Spec<F, T, RATE>, const T: usize, const RATE: usize>(
+pub(crate) fn permute<F: FieldExt, S: Spec<F, T, RATE>, const T: usize, const RATE: usize>(
     state: &mut State<F, T>,
     mds: &Mds<F, T>,
     round_constants: &[[F; T]],