The Goliath birdeater belongs to the tarantula family Theraphosidae. Found in northern South America, it is the largest spider in the world by mass and body length, and second to the giant huntsman spider by leg span. It is also called the Goliath tarantula or Goliath bird-eating spider; the practice of calling theraphosids "bird-eating" derives from an early 18th-century copper engraving by Maria Sibylla Merian that shows one eating a hummingbird. Despite the spider's name, it rarely preys on birds.

Tarantulas comprise a group of large and often hairy spiders of the family Theraphosidae. As of December 2023, 1,100 species have been identified, with 166 genera. The term "tarantula" is usually used to describe members of the family Theraphosidae, although many other members of the same infraorder (Mygalomorphae) are commonly referred to as "tarantulas" or "false tarantulas". Some of the more common species have become popular in the exotic pet trade. Many New World species kept as pets have setae known as urticating hairs that can cause irritation to the skin, and in extreme cases, cause damage to the eyes.