A universal joint (also called a universal coupling or U-joint) is a joint or coupling connecting rigid shafts whose axes are inclined to each other. It is commonly used in shafts that transmit rotary motion. It consists of a pair of hinges located close together, oriented at 90° to each other, connected by a cross shaft. The universal joint is not a constant-velocity joint.

U-joints are also sometimes called by various eponymous names, as follows:

• Cardan joint, after Gerolamo Cardano, a polymath of the 16th century who contributed to knowledge of various clever mechanisms, including gimbals
• Hooke joint or Hooke's joint, after Robert Hooke, a polymath of the 17th century who contributed to knowledge of various clever mechanisms
• Spicer joint, after Clarence W. Spicer and the Spicer Manufacturing Company, who manufactured U joints
• Hardy Spicer joint, after the Hardy Spicer brand, a successor to the Spicer brand