The Thick-billed Honeyguide (Indicator conirostris) is a bird of the honeyguide family Indicatoridae. It has been reported interbreeding with the related Lesser Honeyguide (I. minor) and the two are sometimes treated as a single species.
It is 14-15 centimetres long and has a heavy black bill. The upperparts are yellow-green with dark streaking while the head and underparts are dark greyish, sometimes with faint streaking. The outer tail-feathers are mostly white and there may be a pale spot on the lores. Juvenile birds are similar to adults but are darker and greener. The Lesser Honeyguide is smaller with a less heavy bill. It has a paler head and underparts, less-streaked upperparts and a more conspicuous patch on the lores.
The calls of the Thick-billed Honeyguide include a repeated "frip" which is similar to the call of the Lesser Honeyguide but deeper.
It occurs in parts of West, Central and East Africa. The nominate subspecies is found from southern Nigeria south to north-west Angola and east to Uganda and western Kenya. The form cassini occurs in eastern Sierra Leone, Liberia and southern parts of Guinea, Côte d'Ivoire and Ghana. The species inhabits the interior of dense forest. Where its habitat becomes fragmented it may be replaced by the Lesser Honeyguide which favours more open habitats.
Like other honeyguides, it is a brood parasite laying its eggs in the nests of other birds. The Grey-throated Barbet (Gymnobucco bonapartei) is known to be a host species and other Gymnobucco barbets are probably parasitized as well.