Pyrimidinediones are a class of chemical compounds characterized by a pyrimidine ring substituted with two carbonyl groups.

Examples include naturally occurring metabolites:

Trivial name	IUPAC name	Structure	Pathway
Uracil	Pyrimidine-2,4(1H,3H)-dione		Pyrimidine biosynthesis
Thymine	5-Methylpyrimidine-2,4(1H,3H)-dione		Pyrimidine biosynthesis
	5,6-Diaminopyrimidine-2,4(1H,3H)-dione		Riboflavin biosynthesis

drugs:

• Fluorouracil
• Idoxuridine
• Primidone
• Trifluridine

and pesticides:

• Bromacil
• Saflufenacil