The blue-naped mousebird (Urocolius macrourus), also formerly called the blue-naped coly (Colius macrourus) is a species of bird belonging to the family Coliidae within the order Coliiformes. They are the sister group to the clade Eucavitaves, which contains the families Leptosomiformes (the cuckoo roller), Trogoniformes (trogons), Bucerotiformes (hornbills and hoopoes), Piciformes (woodpeckers, toucans, and barbets) and Coraciformes (kingfishers, bee-eaters, rollers, motmots, and todies).

The species is found in the wild in the drier regions of West Africa to East Africa, as well as Sahel. It is one of the remaining six species of mousebirds. The term "mousebird" comes from its habit of running along branches in a way that resembles the scurrying of a mouse.

The blue-naped mousebird is a fairly small to medium-sized bird, measuring 33–38 cm (13–15 in) in length including the elongated tail of 20–28 cm (7.9–11.0 in), weighing 34–65 g (1.2–2.3 oz). Adults have an ash grey plumage which is darker at top and lighter at bottom. Has a bright turquoise-blue patch on nape and hindneck, long crest, slender and steeply graduated tail, females shorter than males. Both sexes are brown-tinged ash-grey above, greyish-buff below; bare skin on lores and around eyes crimson-red; most of upper mandible crimson-red, rest of bill black; feet purplish red. Juveniles lack the blue on nape, and have pink facial skin and greenish bills, as well as shorter crest.

Characteristic of mousebirds, the blue-naped mousebird has widely spaced and large feet for its body size, which are pamprodactylous; they are able to rotate all four toes to face forward at will. Their toes are strong and dextrous, allowing the birds to climb and scurry along branches, to hang by a toenail, or to use one foot to hold food.