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

Connection methods to pipes include: direct welding (commonly used), flange connection, hot melt connection, electric melt connection, threaded connection, and socket welding connection, etc. According to the production process, they can be classified into: welded elbows, pressed elbows, expanded elbows, cast elbows, and double-welded elbows, etc. Other names: 90-degree elbows, right-angle elbows, etc.