The island monarch (Monarcha cinerascens) is a species of bird in the family Monarchidae. It is found from Sulawesi to the Solomon Islands. Its natural habitats are subtropical or tropical moist lowland forests and subtropical or tropical moist montane forests.

The island monarch was originally described in the genus Drymophila. Alternate names include the grey-headed monarch, island grey-headed monarch, island grey-headed monarch flycatcher and islet monarch.

Ten subspecies are recognized:

The former subspecies nigrirostris from northeastern New Guinea was lumped with impidiens in 2022.