Windmill is a style of pitching in baseball, or more often, softball. It is a form of underhand pitching, where the pitcher rotates his or her arm a complete 360 degrees around its socket before releasing the ball in an underhand throw. In appearance, the arm is like the blade of a windmill, which is what gives this style its name.

Windmill pitching has advantages and disadvantages over normal underhand pitching. The momentum gained while rotating the ball usually makes windmill pitching faster; however, both by swinging one's arm around and by pitching faster, windmill pitching is also a lot harder to control. Many organizations such as Little League Softball allow both types of underhand pitching, even though extra speed exchanged for a loss of control is often a dangerous combination.