Woodpeckers are part of the bird family Picidae, which also includes the piculets, wrynecks and sapsuckers. Members of this family are found worldwide, except for Australia, New Guinea, New Zealand, Madagascar and the extreme polar regions. Most species live in forests or woodland habitats, although a few species are known that live in treeless areas, such as rocky hillsides and deserts, and the Gila woodpecker specialises in exploiting cacti. Woodpeckers are known as the loudest birds of the forest.

Nine families of largely arboreal birds make up the order Piciformes, the best-known of them being the Picidae, which includes the woodpeckers and close relatives. The Piciformes contain about 71 living genera with a little over 450 species, of which the Picidae make up about half.