2-Thiouracil is a chemical derivative of uracil in which the oxygen atom in the 2-position of the ring is substituted by sulfur.

Edwin Astwood used it in 1943 as therapy for Graves' disease for the first time.

[4] Its use in recent times has been replaced by advent of more potent and safer antithyroid drugs.

It occurs in seeds of Brassica and Crucifera species.

Thiouracil has been used as antithyroid, coronary vasodilator, and in congestive heart failure although its use has been largely supplanted by other drugs.