Sethlans was the Etruscan god of smithcraft, of the forge, of the working of bronze and iron. His name is preserved on the Piacenza Liver and on a small number of inscriptions; he is depicted on bronze mirrors as a bearded, often older man, holding the smith's hammer and tongs, frequently wearing a workman's cap (a pilos, the felt cap of the laborer). He was the Etruscan equivalent of the Greek Hephaestus and the Roman Vulcan, and the relationship among the three figures was one of mutual influence over many centuries.

Etruria was a major center of metalwork in the ancient Mediterranean. The iron mines of the island of Elba and the copper deposits of Etruria itself supplied the forges of Populonia, Vetulonia, and the other great Etruscan cities; the Etruscan bronze mirrors, weapons, and statuary that we now admire in museums were the products of those forges. Sethlans was the divine patron of this great metalworking industry, and his cult was particularly developed in the metal-producing cities. Populonia, where the iron-smelting workshops have been excavated, contained a major sanctuary of Sethlans (probably the same as the one Roman sources call the temple of Vulcan).

Sethlans is depicted on a famous mirror with Menrva, watching the birth of Maris (the Etruscan Mars) from the divine egg — a curious mythological scene with no exact Greek or Roman parallel. On another mirror, he is shown with his consort (perhaps the Etruscan version of Aphrodite-Turan), in a domestic scene that emphasizes the homely-divine character of the smith-god rather than his mighty cosmic role.

After the Romanization, Sethlans was simply identified with Vulcan, and his independent character was lost. The Roman cult of Vulcan at the Volcanal in the Forum (one of the oldest Roman cult-sites) was probably already a fusion of indigenous Italian, Etruscan, and Greek elements by the time Cicero wrote about it; Sethlans's contribution to the Roman Vulcan is hard to disentangle, but his presence in the synthesis is reasonably certain.