The Mortimer Trap is a trap in the Berlin Defense of the Ruy Lopez. It is a real trap as it it plays an inferior move trying to induce a mistake by white. It usually arises from this moves

1. e4 e5

2. Nf3 Nc6

3. Bb5 Nf6

4. d3 Ne7

5. Nxe5? c6!

6. Nc4 d6!

7. Ba4 b5