The biceps femoris is a muscle of the thigh located to the posterior, or back. As its name implies, it consists of two heads; the long head is considered part of the hamstring muscle group, while the short head is sometimes excluded from this characterization, as it only causes knee flexion and is activated by a separate nerve.

In anatomy, the thigh is the area between the hip (pelvis) and the knee. Anatomically, it is part of the lower limb.