A tattoo is a marking made by inserting ink into the layers of skin to change the pigment for decorative or other reasons. Tattoos on humans are a type of decorative body modification, while tattoos on animals are most commonly used for identification or branding.

Tattooing has been practiced worldwide. The Ainu, the indigenous people of Japan, traditionally wore facial tattoos. Today one can find Berbers of Tamazgha (North Africa), Maori of New Zealand, and Atayal of Taiwan with facial tattoos. Tattooing was widespread among Polynesian peoples and among certain tribal groups. Despite some taboos surrounding tattooing, the art continues to be popular in many parts of the world.