The moustached hawk-cuckoo (Hierococcyx vagans) is a species of cuckoo in the family Cuculidae.

It is found in Brunei, Indonesia, Laos, Malaysia, Myanmar, and Thailand. Its natural habitat is evergreen and secondary forests. Threatened by habitat loss, it has been assessed as a near-threatened species.

The moustached hawk-cuckoo is 25–30 cm (9.8–11.8 in) long, and it weighs about 58–63 g (2.0–2.2 oz). The crown and nape are grey. The ear coverts are white, and there is a blackish moustache. The back is brown, and the tail has brown bands and a buffy or white tip. The flight feathers have buffy bars. The underparts are creamy-white, with blackish streaks. The eye is dark brown or grey, with a yellow eye-ring around it. The beak is black, and the feet are orange-yellow. The juvenile bird's back and wings are blackish, and it has black streaks on its breast. The fledgling also has a moustache.