diff --git a/.github/workflows/rust.yml b/.github/workflows/rust.yml
index 1a1b27b8fd..670b9dffd1 100644
--- a/.github/workflows/rust.yml
+++ b/.github/workflows/rust.yml
@@ -250,11 +250,11 @@ jobs:
 
       - uses: actions-rs/toolchain@v1
         with:
-          toolchain: "1.65.0"
+          toolchain: "1.66.0"
           override: true
 
       - name: check if README matches MSRV defined here
-        run: grep '1.65.0' src/core/README.md
+        run: grep '1.66.0' src/core/README.md
 
       - name: Check if it builds properly
         uses: actions-rs/cargo@v1
diff --git a/src/core/Cargo.toml b/src/core/Cargo.toml
index ae0c697501..cead811b0a 100644
--- a/src/core/Cargo.toml
+++ b/src/core/Cargo.toml
@@ -11,7 +11,7 @@ edition = "2021"
 readme = "README.md"
 autoexamples = false
 autobins = false
-rust-version = "1.65.0"
+rust-version = "1.66.0"
 
 [lib]
 name = "sourmash"
diff --git a/src/core/README.md b/src/core/README.md
index b71baaabc1..0fa56ad29b 100644
--- a/src/core/README.md
+++ b/src/core/README.md
@@ -38,4 +38,4 @@ Development happens on github at
 
 ## Minimum supported Rust version
 
-Currently the minimum supported Rust version is 1.65.0.
+Currently the minimum supported Rust version is 1.66.0.