The Guadalcanal Thicketbird (Megalurulus whitneyi) is a bird species. Previously placed in the in the "Old World Warbler" family Sylviidae, it does not seem to be a close relative of the typical warblers; probably it belongs in the newly-recognized grass-warbler family Megaluridae. It is found on two Pacific Ocean islands; Guadacanal in the Solomon Islands and Espiritu Santo in Vanuatu. It sometimes includes the Bougainville and Bismarck Thicketbird as subspecies (in which case the 'combined species' is renamed as the Melanesian Thicketbird).

The Guadalcanal Thicketbird is around 16.5 cm long, a slender bird with long legs and a long tail.

Its natural habitats are subtropical or tropical moist lowland forests and subtropical or tropical moist montane forests.