In piping systems, elbows are pipe fittings used to change the direction of the pipeline. Commonly, there are three types based on angles: 45°, 90°, and 180° elbows. Additionally, other non-standard angle elbows, such as 60°, are included based on engineering requirements. 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 (the most common method), flange connection, hot melt connection, electric melt connection, threaded connection, and sleeve connection, etc. They can be categorized by production process into welding elbows, stamping elbows, extruded elbows, cast elbows, and socket welding elbows, etc. Other names: 90-degree elbows, right-angle bends, etc.