diff --git a/Cargo.toml b/Cargo.toml
index 8d14c3d0..a78d0a96 100644
--- a/Cargo.toml
+++ b/Cargo.toml
@@ -1,5 +1,5 @@
 [workspace]
-members = ["field", "insertion", "plonky2", "starky", "system_zero", "util", "waksman", "ecdsa", "u32", "evm"]
+members = ["field", "insertion", "plonky2", "starky", "system_zero", "util", "waksman", "ecdsa", "u32", "evm", "maybe_rayon"]
 
 [profile.release]
 opt-level = 3
diff --git a/maybe_rayon/Cargo.toml b/maybe_rayon/Cargo.toml
new file mode 100644
index 00000000..f8cc95fb
--- /dev/null
+++ b/maybe_rayon/Cargo.toml
@@ -0,0 +1,11 @@
+[package]
+name = "maybe_rayon"
+version = "0.1.0"
+edition = "2021"
+
+# See more keys and their definitions at https://doc.rust-lang.org/cargo/reference/manifest.html
+[features]
+parallel = ["rayon"]
+
+[dependencies]
+rayon = { version = "1.5.3", optional = true }
diff --git a/maybe_rayon/src/lib.rs b/maybe_rayon/src/lib.rs
new file mode 100644
index 00000000..6f8dc7a1
--- /dev/null
+++ b/maybe_rayon/src/lib.rs
@@ -0,0 +1,250 @@
+#[cfg(not(feature = "parallel"))]
+use std::{
+	iter::{IntoIterator, Iterator},
+	slice::{Chunks, ChunksExact, ChunksMut, ChunksExactMut},
+};
+
+#[cfg(feature = "parallel")]
+use rayon::{
+	prelude::*,
+	slice::{Chunks as ParChunks, ChunksMut as ParChunksMut, ChunksExact as ParChunksExact, ChunksExactMut as ParChunksExactMut, ParallelSlice, ParallelSliceMut}
+};
+
+#[cfg(feature = "parallel")]
+pub use rayon::prelude::{
+	ParallelIterator,
+	IndexedParallelIterator,
+	ParallelExtend,
+	ParallelDrainFull,
+	ParallelDrainRange
+};
+
+pub trait MaybeParIter<'data> {
+	#[cfg(feature = "parallel")]
+	type Item: Send + 'data;
+
+	#[cfg(feature = "parallel")]
+	type Iter: ParallelIterator<Item = Self::Item>;
+
+	#[cfg(not(feature = "parallel"))]
+	type Item;
+
+	#[cfg(not(feature = "parallel"))]
+	type Iter: Iterator<Item = Self::Item>;
+
+	fn par_iter(&'data self) -> Self::Iter;
+}
+
+#[cfg(feature = "parallel")]
+impl<'data, T> MaybeParIter<'data> for T where T: ?Sized + IntoParallelRefIterator<'data> {
+	type Item = T::Item;
+	type Iter = T::Iter;
+
+	fn par_iter(&'data self) -> Self::Iter {
+		self.par_iter()
+	}
+}
+
+#[cfg(not(feature = "parallel"))]
+impl<'data, T: 'data> MaybeParIter<'data> for Vec<T> {
+	type Item = &'data T;
+	type Iter = std::slice::Iter<'data, T>;
+
+	fn par_iter(&'data self) -> Self::Iter {
+		self.iter()
+	}
+}
+
+#[cfg(not(feature = "parallel"))]
+impl<'data, T: 'data> MaybeParIter<'data> for [T] {
+	type Item = &'data T;
+	type Iter = std::slice::Iter<'data, T>;
+
+	fn par_iter(&'data self) -> Self::Iter {
+		self.iter()
+	}
+}
+
+pub trait MaybeParIterMut<'data> {
+	#[cfg(feature = "parallel")]
+	type Item: Send + 'data;
+
+	#[cfg(feature = "parallel")]
+	type Iter: ParallelIterator<Item = Self::Item>;
+
+	#[cfg(not(feature = "parallel"))]
+	type Item;
+
+	#[cfg(not(feature = "parallel"))]
+	type Iter: Iterator<Item = Self::Item>;
+
+	fn par_iter_mut(&'data mut self) -> Self::Iter;
+}
+
+#[cfg(feature = "parallel")]
+impl<'data, T> MaybeParIterMut<'data> for T where T: ?Sized + IntoParallelRefMutIterator<'data> {
+	type Item = T::Item;
+	type Iter = T::Iter;
+
+	fn par_iter_mut(&'data mut self) -> Self::Iter {
+		self.par_iter_mut()
+	}
+}
+
+#[cfg(not(feature = "parallel"))]
+impl<'data, T: 'data> MaybeParIterMut<'data> for Vec<T> {
+	type Item = &'data mut T;
+	type Iter = std::slice::IterMut<'data, T>;
+
+	fn par_iter_mut(&'data mut self) -> Self::Iter {
+		self.iter_mut()
+	}
+}
+
+#[cfg(not(feature = "parallel"))]
+impl<'data, T: 'data> MaybeParIterMut<'data> for [T] {
+	type Item = &'data mut T;
+	type Iter = std::slice::IterMut<'data, T>;
+	
+	fn par_iter_mut(&'data mut self) -> Self::Iter {
+		self.iter_mut()
+	}
+}
+
+pub trait MaybeIntoParIter {
+	#[cfg(feature = "parallel")]
+	type Item: Send;
+
+	#[cfg(feature = "parallel")]
+	type Iter: ParallelIterator<Item = Self::Item>;
+
+	#[cfg(not(feature = "parallel"))]
+	type Item;
+
+	#[cfg(not(feature = "parallel"))]
+	type Iter: Iterator<Item = Self::Item>;
+
+	fn maybe_into_par_iter(self) -> Self::Iter;
+}
+
+#[cfg(feature = "parallel")]
+impl<T> MaybeIntoParIter for T where T: IntoParallelIterator {
+	type Item = T::Item;
+	type Iter = T::Iter;
+
+	fn maybe_into_par_iter(self) -> Self::Iter {
+		self.into_par_iter()
+	}
+}
+
+#[cfg(not(feature = "parallel"))]
+impl<T> MaybeIntoParIter for T where T: IntoIterator {
+	type Item = T::Item;
+	type Iter = T::IntoIter;
+
+	fn maybe_into_par_iter(self) -> Self::Iter {
+		self.into_iter()
+	}
+}
+
+#[cfg(feature = "parallel")]
+pub trait MaybeParChunks<T: Sync> {
+	fn par_chunks(&self, chunk_size: usize) -> ParChunks<'_, T>;
+	fn par_chunks_exact(&self, chunk_size: usize) -> ParChunksExact<'_, T>;
+}
+
+#[cfg(not(feature = "parallel"))]
+pub trait MaybeParChunks<T> {
+	fn par_chunks(&self, chunk_size: usize) -> Chunks<'_, T>;
+	fn par_chunks_exact(&self, chunk_size: usize) -> ChunksExact<'_, T>;
+}
+
+#[cfg(feature = "parallel")]
+impl<T: ParallelSlice<U> + ?Sized, U: Sync> MaybeParChunks<U> for T {
+	fn par_chunks(&self, chunk_size: usize) -> ParChunks<'_, U> {
+		self.par_chunks(chunk_size)
+	}
+	fn par_chunks_exact(&self, chunk_size: usize) -> ParChunksExact<'_, U> {
+		self.par_chunks_exact(chunk_size)
+	}
+}
+
+#[cfg(not(feature = "parallel"))]
+impl<T> MaybeParChunks<T> for [T] {
+	fn par_chunks(&self, chunk_size: usize) -> Chunks<'_, T> {
+		self.chunks(chunk_size)
+	}
+
+	fn par_chunks_exact(&self, chunk_size: usize) -> ChunksExact<'_, T> {
+		self.chunks_exact(chunk_size)
+	}
+}
+
+#[cfg(feature = "parallel")]
+pub trait MaybeParChunksMut<T: Send> {
+	fn par_chunks_mut(&mut self, chunk_size: usize) -> ParChunksMut<'_, T>;
+	fn par_chunks_exact_mut(&mut self, chunk_size: usize) -> ParChunksExactMut<'_, T>;
+}
+
+#[cfg(not(feature = "parallel"))]
+pub trait MaybeParChunksMut<T: Send> {
+	fn par_chunks_mut(&mut self, chunk_size: usize) -> ChunksMut<'_, T>;
+	fn par_chunks_exact_mut(&mut self, chunk_size: usize) -> ChunksExactMut<'_, T>;
+}
+
+
+#[cfg(feature = "parallel")]
+impl<T: ?Sized + ParallelSliceMut<U>, U: Send> MaybeParChunksMut<U> for T {
+	fn par_chunks_mut(&mut self, chunk_size: usize) -> ParChunksMut<'_, U> {
+		self.par_chunks_mut(chunk_size)
+	}
+	fn par_chunks_exact_mut(&mut self, chunk_size: usize) -> ParChunksExactMut<'_, U> {
+		self.par_chunks_exact_mut(chunk_size)
+	}
+}
+
+#[cfg(not(feature = "parallel"))]
+impl<T: Send> MaybeParChunksMut<T> for [T] {
+	fn par_chunks_mut(&mut self, chunk_size: usize) -> ChunksMut<'_, T> {
+		self.chunks_mut(chunk_size)
+	}
+	fn par_chunks_exact_mut(&mut self, chunk_size: usize) -> ChunksExactMut<'_, T> {
+		self.chunks_exact_mut(chunk_size)
+	}
+}
+
+pub trait ParallelIteratorMock {
+	type Item;
+	fn find_any<P>(self, predicate: P) -> Option<Self::Item>
+    where
+        P: Fn(&Self::Item) -> bool + Sync + Send;
+}
+
+impl<T: Iterator> ParallelIteratorMock for T {
+	type Item = T::Item;
+
+	fn find_any<P>(mut self, predicate: P) -> Option<Self::Item>
+    where
+        P: Fn(&Self::Item) -> bool + Sync + Send
+	{
+		self.find(predicate)
+	}
+}
+
+#[cfg(feature = "parallel")]
+pub fn join<A, B, RA, RB>(oper_a: A, oper_b: B) -> (RA, RB)
+    where A: FnOnce() -> RA + Send,
+          B: FnOnce() -> RB + Send,
+          RA: Send,
+          RB: Send
+{
+    rayon::join(oper_a, oper_b)
+}
+
+#[cfg(not(feature = "parallel"))]
+pub fn join<A, B, RA, RB>(oper_a: A, oper_b: B) -> (RA, RB)
+    where A: FnOnce() -> RA,
+          B: FnOnce() -> RB,
+{
+    (oper_a(), oper_b())
+}
diff --git a/plonky2/Cargo.toml b/plonky2/Cargo.toml
index 9c019640..9ee89344 100644
--- a/plonky2/Cargo.toml
+++ b/plonky2/Cargo.toml
@@ -10,6 +10,10 @@ categories = ["cryptography"]
 edition = "2021"
 default-run = "generate_constants"
 
+[features]
+default = ["parallel"]
+parallel = ["maybe_rayon/parallel"]
+
 [dependencies]
 plonky2_field = { path = "../field" }
 plonky2_util = { path = "../util" }
@@ -19,7 +23,7 @@ itertools = "0.10.0"
 num = { version = "0.4", features = [ "rand" ] }
 rand = "0.8.4"
 rand_chacha = "0.3.1"
-rayon = "1.5.1"
+maybe_rayon = { path = "../maybe_rayon" }
 unroll = "0.1.5"
 anyhow = "1.0.40"
 serde = { version = "1.0", features = ["derive"] }
@@ -32,6 +36,7 @@ criterion = "0.3.5"
 tynm = "0.1.6"
 structopt = "0.3.26"
 num_cpus = "1.13.1"
+rayon = "1.5.1" 
 
 [target.'cfg(not(target_env = "msvc"))'.dev-dependencies]
 jemallocator = "0.3.2"
diff --git a/plonky2/examples/bench_recursion.rs b/plonky2/examples/bench_recursion.rs
index 1f2d127f..8073c9dc 100644
--- a/plonky2/examples/bench_recursion.rs
+++ b/plonky2/examples/bench_recursion.rs
@@ -2,7 +2,6 @@
 // custom CLI argument parsing (even with harness disabled). We could also have
 // put it in `src/bin/`, but then we wouldn't have access to
 // `[dev-dependencies]`.
-
 #![allow(incomplete_features)]
 #![feature(generic_const_exprs)]
 
diff --git a/plonky2/src/fri/oracle.rs b/plonky2/src/fri/oracle.rs
index 312b458b..da4e9e80 100644
--- a/plonky2/src/fri/oracle.rs
+++ b/plonky2/src/fri/oracle.rs
@@ -5,7 +5,7 @@ use plonky2_field::packed::PackedField;
 use plonky2_field::polynomial::{PolynomialCoeffs, PolynomialValues};
 use plonky2_field::types::Field;
 use plonky2_util::{log2_strict, reverse_index_bits_in_place};
-use rayon::prelude::*;
+use maybe_rayon::*;
 
 use crate::fri::proof::FriProof;
 use crate::fri::prover::fri_proof;
@@ -52,7 +52,7 @@ impl<F: RichField + Extendable<D>, C: GenericConfig<D, F = F>, const D: usize>
         let coeffs = timed!(
             timing,
             "IFFT",
-            values.into_par_iter().map(|v| v.ifft()).collect::<Vec<_>>()
+            values.maybe_into_par_iter().map(|v| v.ifft()).collect::<Vec<_>>()
         );
 
         Self::from_coeffs(
@@ -122,7 +122,7 @@ impl<F: RichField + Extendable<D>, C: GenericConfig<D, F = F>, const D: usize>
             })
             .chain(
                 (0..salt_size)
-                    .into_par_iter()
+                    .maybe_into_par_iter()
                     .map(|_| F::rand_vec(degree << rate_bits)),
             )
             .collect()
diff --git a/plonky2/src/fri/prover.rs b/plonky2/src/fri/prover.rs
index 6136a9a1..0f3215a8 100644
--- a/plonky2/src/fri/prover.rs
+++ b/plonky2/src/fri/prover.rs
@@ -2,7 +2,7 @@ use itertools::Itertools;
 use plonky2_field::extension::{flatten, unflatten, Extendable};
 use plonky2_field::polynomial::{PolynomialCoeffs, PolynomialValues};
 use plonky2_util::reverse_index_bits_in_place;
-use rayon::prelude::*;
+use maybe_rayon::*;
 
 use crate::fri::proof::{FriInitialTreeProof, FriProof, FriQueryRound, FriQueryStep};
 use crate::fri::{FriConfig, FriParams};
@@ -119,7 +119,7 @@ fn fri_proof_of_work<F: RichField + Extendable<D>, C: GenericConfig<D, F = F>, c
     config: &FriConfig,
 ) -> F {
     (0..=F::NEG_ONE.to_canonical_u64())
-        .into_par_iter()
+        .maybe_into_par_iter()
         .find_any(|&i| {
             C::InnerHasher::hash_no_pad(
                 &current_hash
diff --git a/plonky2/src/hash/merkle_tree.rs b/plonky2/src/hash/merkle_tree.rs
index 69cf2ef9..f7b6d4a2 100644
--- a/plonky2/src/hash/merkle_tree.rs
+++ b/plonky2/src/hash/merkle_tree.rs
@@ -2,9 +2,9 @@ use std::mem::MaybeUninit;
 use std::slice;
 
 use plonky2_util::log2_strict;
-use rayon::prelude::*;
 use serde::{Deserialize, Serialize};
 
+use maybe_rayon::*;
 use crate::hash::hash_types::RichField;
 use crate::hash::merkle_proofs::MerkleProof;
 use crate::plonk::config::GenericHashOut;
@@ -77,10 +77,12 @@ where
         let (right_digest_mem, right_digests_buf) = right_digests_buf.split_first_mut().unwrap();
         // Split `leaves` between both children.
         let (left_leaves, right_leaves) = leaves.split_at(leaves.len() / 2);
-        let (left_digest, right_digest) = rayon::join(
+
+        let (left_digest, right_digest) = maybe_rayon::join(
             || fill_subtree::<F, H>(left_digests_buf, left_leaves),
             || fill_subtree::<F, H>(right_digests_buf, right_leaves),
         );
+
         left_digest_mem.write(left_digest);
         right_digest_mem.write(right_digest);
         H::two_to_one(left_digest, right_digest)
diff --git a/plonky2/src/plonk/permutation_argument.rs b/plonky2/src/plonk/permutation_argument.rs
index 076c2a7a..f9b23796 100644
--- a/plonky2/src/plonk/permutation_argument.rs
+++ b/plonky2/src/plonk/permutation_argument.rs
@@ -2,7 +2,7 @@ use std::collections::HashMap;
 
 use plonky2_field::polynomial::PolynomialValues;
 use plonky2_field::types::Field;
-use rayon::prelude::*;
+use maybe_rayon::*;
 
 use crate::iop::target::Target;
 use crate::iop::wire::Wire;
diff --git a/plonky2/src/plonk/proof.rs b/plonky2/src/plonk/proof.rs
index 18af1f73..1cb83b14 100644
--- a/plonky2/src/plonk/proof.rs
+++ b/plonky2/src/plonk/proof.rs
@@ -1,7 +1,7 @@
 use anyhow::ensure;
 use plonky2_field::extension::Extendable;
-use rayon::prelude::*;
 use serde::{Deserialize, Serialize};
+use maybe_rayon::*;
 
 use crate::fri::oracle::PolynomialBatch;
 use crate::fri::proof::{
diff --git a/plonky2/src/plonk/prover.rs b/plonky2/src/plonk/prover.rs
index 26626208..526721f0 100644
--- a/plonky2/src/plonk/prover.rs
+++ b/plonky2/src/plonk/prover.rs
@@ -6,7 +6,7 @@ use plonky2_field::extension::Extendable;
 use plonky2_field::polynomial::{PolynomialCoeffs, PolynomialValues};
 use plonky2_field::zero_poly_coset::ZeroPolyOnCoset;
 use plonky2_util::{ceil_div_usize, log2_ceil};
-use rayon::prelude::*;
+use maybe_rayon::*;
 
 use crate::field::types::Field;
 use crate::fri::oracle::PolynomialBatch;
@@ -142,7 +142,7 @@ where
         timing,
         "split up quotient polys",
         quotient_polys
-            .into_par_iter()
+            .maybe_into_par_iter()
             .flat_map(|mut quotient_poly| {
                 quotient_poly.trim_to_len(quotient_degree).expect(
                     "Quotient has failed, the vanishing polynomial is not divisible by Z_H",
@@ -305,7 +305,7 @@ fn wires_permutation_partial_products_and_zs<
     }
 
     transpose(&all_partial_products_and_zs)
-        .into_par_iter()
+        .maybe_into_par_iter()
         .map(PolynomialValues::new)
         .collect()
 }
@@ -452,7 +452,7 @@ fn compute_quotient_polys<
         .collect();
 
     transpose(&quotient_values)
-        .into_par_iter()
+        .maybe_into_par_iter()
         .map(PolynomialValues::new)
         .map(|values| values.coset_ifft(F::coset_shift()))
         .collect()