What is the longest muscle in the human body?

The sartorius muscle is recognized as the longest muscle in the human body. It runs across the thigh from the hip to the knee, helping with the flexion, abduction, and external rotation of the thigh. Its unique positioning and function allow it to facilitate movements like crossing the legs, which is where it gets its name—derived from the Latin word for tailor, as this action resembles the position tailors would take when sitting.

In contrast, while the rectus femoris is part of the quadriceps group and plays a significant role in knee extension and hip flexion, it is not as lengthy as the sartorius. The latissimus dorsi, although an extensive muscle in terms of surface area and involvement in various arm movements, is not lengthwise the longest. Lastly, the hamstring muscles consist of a group of three muscles located at the back of the thigh rather than being a single muscle, and although they are important for leg movement, they do not surpass the sartorius in terms of length.