diff --git a/halo2_gadgets/Cargo.toml b/halo2_gadgets/Cargo.toml
index 13026f4353..374efda83b 100644
--- a/halo2_gadgets/Cargo.toml
+++ b/halo2_gadgets/Cargo.toml
@@ -9,7 +9,7 @@ authors = [
     "Kris Nuttycombe <kris@electriccoin.co>",
 ]
 edition = "2021"
-rust-version = "1.56.1"
+rust-version = "1.66.0"
 description = "Reusable gadgets and chip implementations for Halo 2"
 license = "MIT OR Apache-2.0"
 repository = "https://github.com/zcash/halo2"
@@ -32,7 +32,7 @@ halo2curves = { version = "0.1.0" }
 proptest = { version = "1.0.0", optional = true }
 rand = "0.8"
 subtle = "2.3"
-uint = "0.9.2" # MSRV 1.56.1
+uint = "0.9.2" 
 
 # Developer tooling dependencies
 plotters = { version = "0.3.0", default-features = false, optional = true }
diff --git a/halo2_proofs/Cargo.toml b/halo2_proofs/Cargo.toml
index 8ced31c0f0..cf62f69ce0 100644
--- a/halo2_proofs/Cargo.toml
+++ b/halo2_proofs/Cargo.toml
@@ -8,7 +8,7 @@ authors = [
     "Jack Grigg <jack@electriccoin.co>",
 ]
 edition = "2021"
-rust-version = "1.56.1"
+rust-version = "1.66.0"
 description = """
 Fast PLONK-based zero-knowledge proving system with no trusted setup
 """
@@ -54,7 +54,7 @@ group = "0.13"
 halo2curves = { version = "0.1.0" }
 rand_core = { version = "0.6", default-features = false }
 tracing = "0.1"
-blake2b_simd = "1"
+blake2b_simd = "1" # MSRV 1.66.0
 sha3 = "0.9.1"
 rand_chacha = "0.3"
 maybe-rayon = { version = "0.1.0", default-features = false }
diff --git a/rust-toolchain b/rust-toolchain
index 902c74186f..b6148bc0a7 100644
--- a/rust-toolchain
+++ b/rust-toolchain
@@ -1 +1 @@
-1.65.0
+1.66.0