Smithson Tennant FRS (November 30, 1761 – February 22, 1815) is an English chemist.

Tennant is best known for his discovery of the elements iridium and osmium, which he finds in the residues from the solution of platinum ores in 1803.

He also contributes to the proof of the identity of diamond and charcoal.

The mineral tennantite is named after him.