Three-way fittings are used for pipe joints and pipeline connectors. Also known as three-way pipe fittings, three-way joints, they are used at the point where a main pipeline branches off.

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