There are seven species of Australasian treecreeper in the passerine bird family Climacteridae. They are medium-small, mostly brown birds with patterning on their underparts, and all are endemic to Australia-New Guinea. They resemble, but are not closely related to, the Holarctic treecreepers. The family is one of several families identified by DNA–DNA hybridisation studies to be part of the Australo-Papuan songbird radiation. There is some molecular support for suggesting that their closest relatives are the large lyrebirds.

A passerine is any bird of the order Passeriformes which includes more than half of all bird species. Sometimes known as perching birds, passerines generally have an anisodactyl arrangement of their toes, which facilitates perching.