diff --git a/zcash_extensions/Cargo.toml b/zcash_extensions/Cargo.toml
index 1bd361caf..14a3f3947 100644
--- a/zcash_extensions/Cargo.toml
+++ b/zcash_extensions/Cargo.toml
@@ -23,6 +23,7 @@ zcash_proofs.workspace = true
 
 [features]
 transparent-inputs = []
+unstable-nu6 = ["zcash_primitives/unstable-nu6"]
 
 [lib]
 bench = false
diff --git a/zcash_extensions/src/transparent/demo.rs b/zcash_extensions/src/transparent/demo.rs
index 640f7e617..1d5b84b99 100644
--- a/zcash_extensions/src/transparent/demo.rs
+++ b/zcash_extensions/src/transparent/demo.rs
@@ -512,6 +512,8 @@ mod tests {
                 NetworkUpgrade::Heartwood => Some(BlockHeight::from_u32(903_800)),
                 NetworkUpgrade::Canopy => Some(BlockHeight::from_u32(1_028_500)),
                 NetworkUpgrade::Nu5 => Some(BlockHeight::from_u32(1_200_000)),
+                #[cfg(feature = "unstable-nu6")]
+                NetworkUpgrade::Nu6 => Some(BlockHeight::from_u32(1_300_000)),
                 NetworkUpgrade::ZFuture => Some(BlockHeight::from_u32(1_400_000)),
             }
         }
diff --git a/zcash_primitives/Cargo.toml b/zcash_primitives/Cargo.toml
index 6147475ba..864684053 100644
--- a/zcash_primitives/Cargo.toml
+++ b/zcash_primitives/Cargo.toml
@@ -106,6 +106,7 @@ multicore = ["bellman/multicore", "orchard/multicore"]
 transparent-inputs = ["hdwallet", "ripemd", "secp256k1"]
 temporary-zcashd = []
 test-dependencies = ["proptest", "orchard/test-dependencies"]
+unstable-nu6 = []
 zfuture = []
 
 [lib]
diff --git a/zcash_primitives/src/consensus.rs b/zcash_primitives/src/consensus.rs
index 7ed52d9bc..f6a734ec4 100644
--- a/zcash_primitives/src/consensus.rs
+++ b/zcash_primitives/src/consensus.rs
@@ -212,6 +212,8 @@ impl Parameters for MainNetwork {
             NetworkUpgrade::Heartwood => Some(BlockHeight(903_000)),
             NetworkUpgrade::Canopy => Some(BlockHeight(1_046_400)),
             NetworkUpgrade::Nu5 => Some(BlockHeight(1_687_104)),
+            #[cfg(feature = "unstable-nu6")]
+            NetworkUpgrade::Nu6 => None,
             #[cfg(feature = "zfuture")]
             NetworkUpgrade::ZFuture => None,
         }
@@ -263,6 +265,8 @@ impl Parameters for TestNetwork {
             NetworkUpgrade::Heartwood => Some(BlockHeight(903_800)),
             NetworkUpgrade::Canopy => Some(BlockHeight(1_028_500)),
             NetworkUpgrade::Nu5 => Some(BlockHeight(1_842_420)),
+            #[cfg(feature = "unstable-nu6")]
+            NetworkUpgrade::Nu6 => None,
             #[cfg(feature = "zfuture")]
             NetworkUpgrade::ZFuture => None,
         }
@@ -393,6 +397,11 @@ pub enum NetworkUpgrade {
     ///
     /// [Nu5]: https://z.cash/upgrade/nu5/
     Nu5,
+    /// The [Nu6] network upgrade.
+    ///
+    /// [Nu6]: https://z.cash/upgrade/nu6/
+    #[cfg(feature = "unstable-nu6")]
+    Nu6,
     /// The ZFUTURE network upgrade.
     ///
     /// This upgrade is expected never to activate on mainnet;
@@ -413,6 +422,8 @@ impl fmt::Display for NetworkUpgrade {
             NetworkUpgrade::Heartwood => write!(f, "Heartwood"),
             NetworkUpgrade::Canopy => write!(f, "Canopy"),
             NetworkUpgrade::Nu5 => write!(f, "Nu5"),
+            #[cfg(feature = "unstable-nu6")]
+            NetworkUpgrade::Nu6 => write!(f, "Nu6"),
             #[cfg(feature = "zfuture")]
             NetworkUpgrade::ZFuture => write!(f, "ZFUTURE"),
         }
@@ -428,6 +439,8 @@ impl NetworkUpgrade {
             NetworkUpgrade::Heartwood => BranchId::Heartwood,
             NetworkUpgrade::Canopy => BranchId::Canopy,
             NetworkUpgrade::Nu5 => BranchId::Nu5,
+            #[cfg(feature = "unstable-nu6")]
+            NetworkUpgrade::Nu6 => BranchId::Nu6,
             #[cfg(feature = "zfuture")]
             NetworkUpgrade::ZFuture => BranchId::ZFuture,
         }
@@ -445,6 +458,8 @@ const UPGRADES_IN_ORDER: &[NetworkUpgrade] = &[
     NetworkUpgrade::Heartwood,
     NetworkUpgrade::Canopy,
     NetworkUpgrade::Nu5,
+    #[cfg(feature = "unstable-nu6")]
+    NetworkUpgrade::Nu6,
 ];
 
 pub const ZIP212_GRACE_PERIOD: u32 = 32256;
@@ -478,6 +493,9 @@ pub enum BranchId {
     Canopy,
     /// The consensus rules deployed by [`NetworkUpgrade::Nu5`].
     Nu5,
+    /// The consensus rules deployed by [`NetworkUpgrade::Nu6`].
+    #[cfg(feature = "unstable-nu6")]
+    Nu6,
     /// Candidates for future consensus rules; this branch will never
     /// activate on mainnet.
     #[cfg(feature = "zfuture")]
@@ -498,6 +516,8 @@ impl TryFrom<u32> for BranchId {
             0xf5b9_230b => Ok(BranchId::Heartwood),
             0xe9ff_75a6 => Ok(BranchId::Canopy),
             0xc2d6_d0b4 => Ok(BranchId::Nu5),
+            #[cfg(feature = "unstable-nu6")]
+            0xc8e7_1055 => Ok(BranchId::Nu6),
             #[cfg(feature = "zfuture")]
             0xffff_ffff => Ok(BranchId::ZFuture),
             _ => Err("Unknown consensus branch ID"),
@@ -515,6 +535,8 @@ impl From<BranchId> for u32 {
             BranchId::Heartwood => 0xf5b9_230b,
             BranchId::Canopy => 0xe9ff_75a6,
             BranchId::Nu5 => 0xc2d6_d0b4,
+            #[cfg(feature = "unstable-nu6")]
+            BranchId::Nu6 => 0xc8e7_1055,
             #[cfg(feature = "zfuture")]
             BranchId::ZFuture => 0xffff_ffff,
         }
@@ -587,6 +609,8 @@ impl BranchId {
                 let upper = None;
                 (lower, upper)
             }),
+            #[cfg(feature = "unstable-nu6")]
+            BranchId::Nu6 => None,
             #[cfg(feature = "zfuture")]
             BranchId::ZFuture => params
                 .activation_height(NetworkUpgrade::ZFuture)
@@ -634,6 +658,8 @@ pub mod testing {
             BranchId::Heartwood,
             BranchId::Canopy,
             BranchId::Nu5,
+            #[cfg(feature = "unstable-nu6")]
+            BranchId::Nu6,
             #[cfg(feature = "zfuture")]
             BranchId::ZFuture,
         ])
diff --git a/zcash_primitives/src/transaction/mod.rs b/zcash_primitives/src/transaction/mod.rs
index b9ff932af..13bd24a2d 100644
--- a/zcash_primitives/src/transaction/mod.rs
+++ b/zcash_primitives/src/transaction/mod.rs
@@ -239,6 +239,8 @@ impl TxVersion {
                 TxVersion::Sapling
             }
             BranchId::Nu5 => TxVersion::Zip225,
+            #[cfg(feature = "unstable-nu6")]
+            BranchId::Nu6 => TxVersion::Zip225,
             #[cfg(feature = "zfuture")]
             BranchId::ZFuture => TxVersion::ZFuture,
         }
@@ -970,6 +972,8 @@ pub mod testing {
                 Just(TxVersion::Sapling).boxed()
             }
             BranchId::Nu5 => Just(TxVersion::Zip225).boxed(),
+            #[cfg(feature = "unstable-nu6")]
+            BranchId::Nu6 => Just(TxVersion::Zip225).boxed(),
             #[cfg(feature = "zfuture")]
             BranchId::ZFuture => Just(TxVersion::ZFuture).boxed(),
         }