A U-turn in driving refers to performing a 180° rotation to reverse the direction of travel. It is called a "U-turn" because the maneuver looks like the letter U. In some areas, the maneuver is illegal, while in others, it is treated as a more ordinary turn, merely extended. In still other areas, lanes are occasionally marked "U-turn permitted" or even "U-turn only."

Occasionally, on a divided highway, special U-turn ramps exist to allow traffic to make a U-turn, though often their use is restricted to emergency and police vehicles only.

In the United States, U-turn regulations vary by state: in Indiana U-turns are allowed as long as the driver follows all of the precautions normally ascribed to making a left turn (yielding right-of-way, etc.). Many places, including Texas and Georgia, have specially designed U-turn lanes (referred to as Texas U-turn lanes). In Michigan, U-turns are required for many left turns to and from divided highways, as part of the Michigan left maneuver.

In some special situations, U-turns can be regulated through the use of a traffic light, where it is the only directional choice and drivers in the specified lane cannot continue forward (“U-turn only” lanes).