diff --git a/clippy.toml b/clippy.toml
index 70096057..38037a01 100644
--- a/clippy.toml
+++ b/clippy.toml
@@ -49,6 +49,8 @@ disallowed-methods = [
     { path = 'tokio::fs::write',            reason = 'use fs_err::tokio::write for more helpful error messages'            },
 
     { path = 'axum::Router::nest', reason = 'specify full resource paths for searchability' },
+
+    { path = 'itertools::repeat_n', reason = 'use core::iter::repeat_n' },
 ]
 disallowed-types = [
     { path = 'std::fs::DirEntry',      reason = 'use fs_err::DirEntry for more helpful error messages'           },
diff --git a/fork_choice_store/src/store.rs b/fork_choice_store/src/store.rs
index 65c3d139..0cc07dd5 100644
--- a/fork_choice_store/src/store.rs
+++ b/fork_choice_store/src/store.rs
@@ -248,7 +248,7 @@ impl<P: Preset> Store<P> {
         };
 
         let validator_count = anchor_state.validators().len_usize();
-        let latest_messages = itertools::repeat_n(None, validator_count).collect();
+        let latest_messages = core::iter::repeat_n(None, validator_count).collect();
 
         Self {
             chain_config,
@@ -2446,7 +2446,7 @@ impl<P: Preset> Store<P> {
     fn extend_latest_messages_after_finalization(&mut self) {
         let old_length = self.latest_messages.len();
         let new_length = self.last_finalized().state(self).validators().len_usize();
-        let added_vacancies = itertools::repeat_n(None, new_length - old_length);
+        let added_vacancies = core::iter::repeat_n(None, new_length - old_length);
 
         self.latest_messages.extend(added_vacancies);
     }
diff --git a/ssz/src/contiguous_vector.rs b/ssz/src/contiguous_vector.rs
index eab27ae5..e626b4b9 100644
--- a/ssz/src/contiguous_vector.rs
+++ b/ssz/src/contiguous_vector.rs
@@ -159,7 +159,7 @@ impl<T, N: ArrayLength<T>> ContiguousVector<T, N> {
     where
         T: Clone,
     {
-        Self::try_from_iter(itertools::repeat_n(element, N::USIZE))
+        Self::try_from_iter(core::iter::repeat_n(element, N::USIZE))
             .expect("length of iterator matches type parameter")
     }
 }
diff --git a/ssz/src/merkle_tree.rs b/ssz/src/merkle_tree.rs
index 6d6d8005..d6187884 100644
--- a/ssz/src/merkle_tree.rs
+++ b/ssz/src/merkle_tree.rs
@@ -393,12 +393,12 @@ mod tests {
         let ff_hash_1 = hashing::hash_256_256(ff_hash_0, ff_hash_0);
         let ff_hash_2 = hashing::hash_256_256(ff_hash_1, ff_hash_1);
 
-        let chunks = itertools::repeat_n(ff_hash_0, capacity);
+        let chunks = core::iter::repeat_n(ff_hash_0, capacity);
         let chunk_indices = 0..capacity;
         let proof_indices = chunk_indices.clone();
 
         let expected_proof = [ff_hash_0, ff_hash_1, ff_hash_2, hash_of_length(capacity)].into();
-        let expected_proofs = itertools::repeat_n(expected_proof, capacity);
+        let expected_proofs = core::iter::repeat_n(expected_proof, capacity);
 
         let actual_proofs = MerkleTree::<Depth>::default().extend_and_construct_proofs(
             chunks,
diff --git a/transition_functions/src/altair/epoch_intermediates.rs b/transition_functions/src/altair/epoch_intermediates.rs
index 7f4a3294..cee7b58c 100644
--- a/transition_functions/src/altair/epoch_intermediates.rs
+++ b/transition_functions/src/altair/epoch_intermediates.rs
@@ -366,12 +366,12 @@ mod spec_tests {
 
         TestDeltas::assert_equal(
             epoch_deltas.iter().map(|deltas| deltas.head_reward),
-            itertools::repeat_n(0, epoch_deltas.len()),
+            core::iter::repeat_n(0, epoch_deltas.len()),
             case.ssz_default("head_deltas"),
         );
 
         TestDeltas::assert_equal(
-            itertools::repeat_n(0, epoch_deltas.len()),
+            core::iter::repeat_n(0, epoch_deltas.len()),
             epoch_deltas.iter().map(|deltas| deltas.inactivity_penalty),
             case.ssz_default("inactivity_penalty_deltas"),
         );
diff --git a/transition_functions/src/bellatrix/epoch_intermediates.rs b/transition_functions/src/bellatrix/epoch_intermediates.rs
index 790c80f1..1575a50a 100644
--- a/transition_functions/src/bellatrix/epoch_intermediates.rs
+++ b/transition_functions/src/bellatrix/epoch_intermediates.rs
@@ -148,12 +148,12 @@ mod spec_tests {
 
         TestDeltas::assert_equal(
             epoch_deltas.iter().map(|deltas| deltas.head_reward),
-            itertools::repeat_n(0, epoch_deltas.len()),
+            core::iter::repeat_n(0, epoch_deltas.len()),
             case.ssz_default("head_deltas"),
         );
 
         TestDeltas::assert_equal(
-            itertools::repeat_n(0, epoch_deltas.len()),
+            core::iter::repeat_n(0, epoch_deltas.len()),
             epoch_deltas.iter().map(|deltas| deltas.inactivity_penalty),
             case.ssz_default("inactivity_penalty_deltas"),
         );
diff --git a/transition_functions/src/capella/epoch_intermediates.rs b/transition_functions/src/capella/epoch_intermediates.rs
index b790e2a6..be56b3f1 100644
--- a/transition_functions/src/capella/epoch_intermediates.rs
+++ b/transition_functions/src/capella/epoch_intermediates.rs
@@ -148,12 +148,12 @@ mod spec_tests {
 
         TestDeltas::assert_equal(
             epoch_deltas.iter().map(|deltas| deltas.head_reward),
-            itertools::repeat_n(0, epoch_deltas.len()),
+            core::iter::repeat_n(0, epoch_deltas.len()),
             case.ssz_default("head_deltas"),
         );
 
         TestDeltas::assert_equal(
-            itertools::repeat_n(0, epoch_deltas.len()),
+            core::iter::repeat_n(0, epoch_deltas.len()),
             epoch_deltas.iter().map(|deltas| deltas.inactivity_penalty),
             case.ssz_default("inactivity_penalty_deltas"),
         );
diff --git a/transition_functions/src/deneb/epoch_intermediates.rs b/transition_functions/src/deneb/epoch_intermediates.rs
index 495a5fa5..199c8896 100644
--- a/transition_functions/src/deneb/epoch_intermediates.rs
+++ b/transition_functions/src/deneb/epoch_intermediates.rs
@@ -148,12 +148,12 @@ mod spec_tests {
 
         TestDeltas::assert_equal(
             epoch_deltas.iter().map(|deltas| deltas.head_reward),
-            itertools::repeat_n(0, epoch_deltas.len()),
+            core::iter::repeat_n(0, epoch_deltas.len()),
             case.ssz_default("head_deltas"),
         );
 
         TestDeltas::assert_equal(
-            itertools::repeat_n(0, epoch_deltas.len()),
+            core::iter::repeat_n(0, epoch_deltas.len()),
             epoch_deltas.iter().map(|deltas| deltas.inactivity_penalty),
             case.ssz_default("inactivity_penalty_deltas"),
         );
diff --git a/transition_functions/src/electra/epoch_intermediates.rs b/transition_functions/src/electra/epoch_intermediates.rs
index d98ea1d7..02b67a2b 100644
--- a/transition_functions/src/electra/epoch_intermediates.rs
+++ b/transition_functions/src/electra/epoch_intermediates.rs
@@ -148,12 +148,12 @@ mod spec_tests {
 
         TestDeltas::assert_equal(
             epoch_deltas.iter().map(|deltas| deltas.head_reward),
-            itertools::repeat_n(0, epoch_deltas.len()),
+            core::iter::repeat_n(0, epoch_deltas.len()),
             case.ssz_default("head_deltas"),
         );
 
         TestDeltas::assert_equal(
-            itertools::repeat_n(0, epoch_deltas.len()),
+            core::iter::repeat_n(0, epoch_deltas.len()),
             epoch_deltas.iter().map(|deltas| deltas.inactivity_penalty),
             case.ssz_default("inactivity_penalty_deltas"),
         );
diff --git a/transition_functions/src/phase0/epoch_intermediates.rs b/transition_functions/src/phase0/epoch_intermediates.rs
index 8b9c712e..c7b419f3 100644
--- a/transition_functions/src/phase0/epoch_intermediates.rs
+++ b/transition_functions/src/phase0/epoch_intermediates.rs
@@ -818,12 +818,12 @@ mod spec_tests {
             deltas
                 .iter()
                 .map(|deltas| deltas.proposer_reward + deltas.inclusion_delay_reward),
-            itertools::repeat_n(0, deltas.len()),
+            core::iter::repeat_n(0, deltas.len()),
             case.ssz_default("inclusion_delay_deltas"),
         );
 
         TestDeltas::assert_equal(
-            itertools::repeat_n(0, deltas.len()),
+            core::iter::repeat_n(0, deltas.len()),
             deltas
                 .iter()
                 .map(|deltas| deltas.canceling_penalty + deltas.inactivity_penalty),