Quinazolinone is a heterocyclic chemical compound, a quinazoline with a carbonyl group in the C4N2 ring.

Two isomers are possible: 2-quinazolinone and 4-quinazolinone, with the 4-isomer being the more common.

These compounds are of interest in medicinal chemistry.

[1] Common routes to quinazolines involve condensation of amides to anilines with ortho nitrile, carboxylic acids and amides.

[2] Quinazolinone drugs that function as hypnotic/sedatives, methaqualone (Quaalude) for example, usually contain a 4-quinazolinone core with a 2-substituted phenyl group at nitrogen atom 3.