The grey-bellied cuckoo or the Indian plaintive cuckoo (Cacomantis passerinus) is a cuckoo with widespread occurrence throughout Asia.
The grey-bellied cuckoo is one of the smaller cuckoos, at a total length of about 23 cm. Adults are mainly grey with a white lower belly and undertail. There is a white patch on the wings. Some females are dark-barred reddish brown above with an unbarred tail and have strongly dark-barred whitish underparts. The juvenile resembles the female but is of a duller grey.