A fluid coupling or hydraulic coupling is a hydrodynamic device used to transmit rotating mechanical power. It has been used in automobile transmissions as an alternative to a mechanical clutch.

A quick connect fitting, also called a quick disconnect or quick release coupling, is a coupling used to provide a fast, make-or-break connection of fluid transfer lines. Operated by hand, quick connect fittings replace threaded or flanged connections, which require wrenches.