In piping systems, elbows are fittings that change the direction of the pipeline. Commonly available in angles of 45°, 90°, and 180°, there are also other non-standard angle elbows, such as 60°, as needed for engineering purposes. Materials for elbows include cast iron, stainless steel, alloy steel, malleable cast iron, carbon steel, non-ferrous metals, and plastics.

Ways to connect pipes include direct welding (common method), flange connection, hot melt connection, electric melt connection, threaded connection, and socket welding connection, etc. They can be categorized by production process into welded elbows, stamped elbows, extruded elbows, cast elbows, and socket-welded elbows, etc. Other names: 90-degree elbows, right-angle elbows, etc.