diff --git a/Cargo.lock b/Cargo.lock
index b70f2b25..17ed3526 100644
--- a/Cargo.lock
+++ b/Cargo.lock
@@ -779,6 +779,7 @@ name = "p521"
 version = "0.13.0"
 dependencies = [
  "base16ct",
+ "blobby",
  "ecdsa",
  "elliptic-curve",
  "hex-literal",
diff --git a/p521/Cargo.toml b/p521/Cargo.toml
index bd3b9a68..513421dc 100644
--- a/p521/Cargo.toml
+++ b/p521/Cargo.toml
@@ -27,6 +27,7 @@ rand_core = { version = "0.6", optional = true, default-features = false }
 sha2 = { version = "0.10", optional = true, default-features = false }
 
 [dev-dependencies]
+blobby = "0.3"
 ecdsa-core = { version = "0.16", package = "ecdsa", default-features = false, features = ["dev"] }
 hex-literal = "0.4"
 primeorder = { version = "0.13.3", features = ["dev"], path = "../primeorder" }
diff --git a/p521/src/ecdsa.rs b/p521/src/ecdsa.rs
index aafa4695..659aeed1 100644
--- a/p521/src/ecdsa.rs
+++ b/p521/src/ecdsa.rs
@@ -241,9 +241,89 @@ mod tests {
         ecdsa_core::new_verification_test!(NistP521, ECDSA_TEST_VECTORS);
     }
 
-    // TODO(tarcieri): wycheproof test vectors
-    // mod wycheproof {
-    //     use crate::NistP521;
-    //     ecdsa_core::new_wycheproof_test!(wycheproof, "wycheproof", NistP521);
-    // }
+    mod wycheproof {
+        use crate::{
+            ecdsa::{Signature, Verifier, VerifyingKey},
+            EncodedPoint, NistP521,
+        };
+
+        // TODO: use ecdsa_core::new_wycheproof_test!(wycheproof, "wycheproof", NistP521);
+        #[test]
+        fn wycheproof() {
+            use blobby::Blob5Iterator;
+            use elliptic_curve::generic_array::typenum::Unsigned;
+
+            // Build a field element but allow for too-short input (left pad with zeros)
+            // or too-long input (check excess leftmost bytes are zeros).
+            fn element_from_padded_slice<C: elliptic_curve::Curve>(
+                data: &[u8],
+            ) -> elliptic_curve::FieldBytes<C> {
+                let point_len = C::FieldBytesSize::USIZE;
+                if data.len() >= point_len {
+                    let offset = data.len() - point_len;
+                    for v in data.iter().take(offset) {
+                        assert_eq!(*v, 0, "EcdsaVerifier: point too large");
+                    }
+                    elliptic_curve::FieldBytes::<C>::clone_from_slice(&data[offset..])
+                } else {
+                    // Provided slice is too short and needs to be padded with zeros
+                    // on the left.  Build a combined exact iterator to do this.
+                    let iter = core::iter::repeat(0)
+                        .take(point_len - data.len())
+                        .chain(data.iter().cloned());
+                    elliptic_curve::FieldBytes::<C>::from_exact_iter(iter).unwrap()
+                }
+            }
+
+            fn run_test(
+                wx: &[u8],
+                wy: &[u8],
+                msg: &[u8],
+                sig: &[u8],
+                pass: bool,
+            ) -> Option<&'static str> {
+                let x = element_from_padded_slice::<NistP521>(wx);
+                let y = element_from_padded_slice::<NistP521>(wy);
+                let q_encoded =
+                    EncodedPoint::from_affine_coordinates(&x, &y, /* compress= */ false);
+                let verifying_key = VerifyingKey::from_encoded_point(&q_encoded).unwrap();
+
+                let sig = match Signature::from_der(sig) {
+                    Ok(s) => s,
+                    Err(_) if !pass => return None,
+                    Err(_) => return Some("failed to parse signature ASN.1"),
+                };
+
+                match verifying_key.verify(msg, &sig) {
+                    Ok(_) if pass => None,
+                    Ok(_) => Some("signature verify unexpectedly succeeded"),
+                    Err(_) if !pass => None,
+                    Err(_) => Some("signature verify failed"),
+                }
+            }
+
+            let data = include_bytes!(concat!("test_vectors/data/wycheproof.blb"));
+
+            for (i, row) in Blob5Iterator::new(data).unwrap().enumerate() {
+                let [wx, wy, msg, sig, status] = row.unwrap();
+                let pass = match status[0] {
+                    0 => false,
+                    1 => true,
+                    _ => panic!("invalid value for pass flag"),
+                };
+                if let Some(desc) = run_test(wx, wy, msg, sig, pass) {
+                    panic!(
+                        "\n\
+                                 Failed test №{}: {}\n\
+                                 wx:\t{:?}\n\
+                                 wy:\t{:?}\n\
+                                 msg:\t{:?}\n\
+                                 sig:\t{:?}\n\
+                                 pass:\t{}\n",
+                        i, desc, wx, wy, msg, sig, pass,
+                    );
+                }
+            }
+        }
+    }
 }
diff --git a/p521/src/test_vectors/data/wycheproof.blb b/p521/src/test_vectors/data/wycheproof.blb
new file mode 100644
index 00000000..2ab50eab
Binary files /dev/null and b/p521/src/test_vectors/data/wycheproof.blb differ