A tattoo is a marking made by inserting indelible 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), Māori of New Zealand, Arabic people in East-Turkey and Atayal of Taiwan with facial tattoos. Tattooing was widespread among Polynesian peoples and among certain tribal groups in the Taiwan, Philippines, Borneo, Mentawai Islands, Africa, North America, South America, Mesoamerica, Europe, Japan, Cambodia, New Zealand and Micronesia. Despite some taboos surrounding tattooing, the art continues to be popular in many parts of the world.