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.
M. c. commutatus - Brüggemann, 1876: Originally described as a separate species. Found on Sangir, Siau, Mayu and Tifore Islands (off north-eastern Sulawesi)
M. c. inornatus - (Lesson, R & Garnot, 1828): Originally described as a separate species in the genus Muscicapa. Found on western Papuan islands, north-western New Guinea and Aru Islands