A passerine is a bird of the order Passeriformes, which includes more than half of all bird species. Sometimes known as perching birds or, less accurately, as songbirds, the passerines form one of the most diverse terrestrial vertebrate orders; with over 5,000 identified species, it has roughly twice as many species as the largest of the mammal orders, the Rodentia. It contains more than 110 families, the second most of any order of vertebrates (after the Perciformes).

The names "passerines" and "Passeriformes" are derived from Passer domesticus, the scientific name of the eponymous species (the House Sparrow) and ultimately from the Latin term passer for Passer sparrows and similar small birds.