Stereolithography (SLA®) is an additive manufacturing process in which a UV laser traces a cross section of the part onto a vat of UV-curable liquid photopolymer resin, hardening the resin. Each successive cross section is traced onto the resin, and the part builds up layer by layer.

SLA is great for concept models, rapid prototypes, master patterns, snap fit assemblies, form-and-fit testing and tradeshow models.

Stereolithography (SLA or SL; also known as optical fabrication, photo-solidification, solid free-form fabrication, solid imaging and Resin printing) is an additive manufacturing process which employs a vat of liquid ultraviolet curable photopolymer "resin" and an ultraviolet laser to build parts' layers one at a time. For each layer, the laser beam traces a cross-section of the part pattern on the surface of the liquid resin. Exposure to the ultraviolet laser light cures and solidifies the pattern traced on the resin and joins it to the layer below.

Chuck Hull founder of 3D Systems is the inventor and patent-holder of the first stereolithography (SLA) rapid prototyping system.