Vastus Lateralis
| Pronuncation | lat-er-AL-iss |
| Derivation | The vast muscle on the lateral side of the thigh. |
| Origin | Front surface on the upper end of the femur. The belly wraps around the lateral side of the femur and attaches to a long line on the back. |
| Insertion | Patellar tendon. |
| Action | Straightens the leg at the knee. |
Vastus lateralis is a wide muscle. Its ends lie forward on the thigh, but its middle extends across most of the lateral side.
It lies under the whole of the iliotibial band, and a break may be seen at its forward edge.