6-propyl-2-thiouracil is a pyrimidinethione consisting of uracil in which the 2-oxo group is substituted by a thio group and the hydrogen at position 6 is substituted by a propyl group. It has a role as an antithyroid drug, a carcinogenic agent, an antimetabolite, a hormone antagonist, an EC 1.14.13.39 (nitric oxide synthase) inhibitor, an antioxidant and an antidote to paracetamol poisoning. It derives from a uracil.