diff --git a/ssz-rs/Cargo.toml b/ssz-rs/Cargo.toml
index 36f11cea..bb454018 100644
--- a/ssz-rs/Cargo.toml
+++ b/ssz-rs/Cargo.toml
@@ -13,6 +13,7 @@ exclude = ["tests/data"]
 
 [features]
 default = ["serde", "std"]
+hashtree = ["dep:hashtree"]
 std = ["bitvec/default", "sha2/default", "alloy-primitives/default"]
 sha2-asm = ["sha2/asm"]
 serde = ["dep:serde", "alloy-primitives/serde"]
@@ -20,6 +21,7 @@ serde = ["dep:serde", "alloy-primitives/serde"]
 [dependencies]
 bitvec = { version = "1.0.0", default-features = false, features = ["alloc"] }
 rayon = "1.10"
+hashtree = { version = "0.2.0", optional = true, package = "hashtree-rs" }
 ssz_rs_derive = { path = "../ssz-rs-derive", version = "0.9.0" }
 sha2 = { version = "0.9.8", default-features = false }
 serde = { version = "1.0", default-features = false, features = [
diff --git a/ssz-rs/src/merkleization/hasher.rs b/ssz-rs/src/merkleization/hasher.rs
index 2698ef2c..fc1d9d62 100644
--- a/ssz-rs/src/merkleization/hasher.rs
+++ b/ssz-rs/src/merkleization/hasher.rs
@@ -1,8 +1,41 @@
+#[cfg(feature = "hashtree")]
+use std::sync::Once;
+
 use super::BYTES_PER_CHUNK;
 
+#[cfg(not(feature = "hashtree"))]
 use ::sha2::{Digest, Sha256};
 
+#[cfg(feature = "hashtree")]
+static INIT: Once = Once::new();
+
+#[inline]
+#[cfg(feature = "hashtree")]
+fn hash_chunks_hashtree(left: impl AsRef<[u8]>, right: impl AsRef<[u8]>) -> [u8; BYTES_PER_CHUNK] {
+    // Initialize the hashtree library (once)
+    INIT.call_once(|| {
+        hashtree::init();
+    });
+
+    let mut out = [0u8; BYTES_PER_CHUNK];
+
+    let mut chunks = [0u8; 2 * BYTES_PER_CHUNK];
+
+    chunks[..BYTES_PER_CHUNK].copy_from_slice(left.as_ref());
+    chunks[BYTES_PER_CHUNK..].copy_from_slice(right.as_ref());
+
+    // NOTE: hashtree "chunks" are 64 bytes long, not 32. That's why we
+    // specify "1" as the chunk count.
+    hashtree::hash(&mut out, &chunks, 1);
+
+    out
+}
+
+// Hashes two chunks together using sha256
+// Defaults to sha256
+// sha256-asm can be enabled with the "sha2-asm" feature flag
 #[inline]
+#[cfg(not(feature = "hashtree"))]
 fn hash_chunks_sha256(left: impl AsRef<[u8]>, right: impl AsRef<[u8]>) -> [u8; BYTES_PER_CHUNK] {
     let mut hasher = Sha256::new();
     hasher.update(left.as_ref());
@@ -13,11 +46,16 @@ fn hash_chunks_sha256(left: impl AsRef<[u8]>, right: impl AsRef<[u8]>) -> [u8; B
 /// Function that hashes 2 [BYTES_PER_CHUNK] (32) len byte slices together. Depending on the feature
 /// flags, this will either use:
 /// - sha256 (default)
-/// - TODO: sha256 with assembly support (with the "sha2-asm" feature flag)
-/// - TODO: hashtree (with the "hashtree" feature flag)
+/// - sha256 with assembly support (with the "sha2-asm" feature flag)
+/// - hashtree (with the "hashtree" feature flag)
 #[inline]
 pub fn hash_chunks(left: impl AsRef<[u8]>, right: impl AsRef<[u8]>) -> [u8; BYTES_PER_CHUNK] {
     debug_assert!(left.as_ref().len() == BYTES_PER_CHUNK);
     debug_assert!(right.as_ref().len() == BYTES_PER_CHUNK);
-    hash_chunks_sha256(left, right)
+
+    #[cfg(feature = "hashtree")]
+    return hash_chunks_hashtree(left, right);
+
+    #[cfg(not(feature = "hashtree"))]
+    return hash_chunks_sha256(left, right);
 }