Three-way fittings are used for pipe joints and pipeline connectors. Also known as pipe fitting three-way, three-way pipe fitting, or three-way joint, they are used where the main pipeline needs to branch off.

A three-way is a type of industrial piping fitting with three openings: one inlet and two outlets; or two inlets and one outlet. It comes in T-shaped and Y-shaped designs, with both equal and unequal diameter pipe ends, used at junctions where three pipes, either the same or different, converge. The primary function of a three-way is to alter the direction of fluid flow.