A tattoo is a design or marking made by the insertion of a pigment into punctures or cuts in the skin. In technical terms, tattooing is micro-pigment implantation. Tattoos are a type of body modification.

The word is traced to the Tahitian tatu or tatau, meaning to mark or strike (the latter referring to traditional methods of applying the designs). In Japanese the word used for traditional designs or those that are applied using traditional methods is irezumi ("insertion of ink"), while "tattoo" is used for non-Japanese designs.

Most tattoo enthusiasts refer to tattoos as tats, ink, art or work, and to tattooists as artists. This usage is gaining support, with mainstream art galleries holding exhibitions of tattoo designs and photographs of tattoos.

Tattoo designs that are mass produced and sold to tattoo artists and studios and displayed in shop are known as flash.

Prevalence
Tattoos have become popular in recent decades in many parts of the world, particularly in North America, Japan, and Europe. The growth in tattoo culture has seen an influx of new artists into the industry, many of whom have technical and fine art training. Coupled with advancements in tattoo pigments and the ongoing refinement of the equipment used for tattooing, this has led to an improvement in the quality of tattoos being produced. Movie stars, models, popular musicians and sports figures are just some of the people in the public eye who are tattooed, which in turn has fuelled the acceptance of tattoos.

In many traditional cultures tattooing has enjoyed a resurgence, partially in deference to their cultural heritage. Historically, a decline in traditional tribal tattooing in Europe occurred with the spread of Christianity. A decline often occurred in other cultures following European efforts to convert aboriginal and indigenous people to Western religious and cultural practices that held tattooing to be a "pagan" or "heathen" activity. Within some traditional indigenous cultures, tattooing takes place within the context of a rite of passage between adolescence and adulthood.

Diversity
Tattooing has been a nearly ubiquitous human practice. The Ainu, the indigenous people of Japan, wore facial tattoos. Tattooing was widespread among Polynesian peoples, and in the Philippines, Borneo, Africa, North America, South America, Mesoamerica, Europe, Japan, and China.

Tattooing in prehistoric times
Tattooing has been a Eurasian practice since Neolithic times. "Ötzi the Iceman", dated circa 3300 BC, exhibits possible therapeutic tattoos (small parallel dashes along lumbar and on the legs). Tarim Basin (West China, Xinjiang) revealed several tattooed mummies of a Western (Western Asian/European) physical type. Still relatively unknown (the only current publications in Western languages are those of J P. Mallory and V H. Mair, The Tarim Mummies, London, 2000), some of them could date from the end of the 2nd millennium BCE.

Three tattooed mummies (c. 300 BCE) were extracted from the permafrost of Altaï in the second half of the 20th century (the Man of Payzyrk, during the 1940s; one female mummy and one male in Ukok plateau, during the 1990s). Their tattooing involved animal designs carried out in a curvilinear style. The Man of Pazyryk was also tattooed with dots that lined up along the spinal column (lumbar region) and around the right ankle.