1. The outermost of the three large gluteus muscles that form each buttock in humans.
2. The greatest gluteal muscle and the biggest muscle in the human body.

The gluteus maximus forms most of the buttocks and it acts to extend the upper leg, spread it, and turn it outward.

There are two other gluteal muscles called the gluteus medius and the gluteus minimus. Together with the gluteus maximus, they are the muscles on which we sit.