There isn’t a single exact count, but scientists estimate there are about 7.7 million animal species on Earth, with roughly 1.7 million species already described by science. Another widely cited estimate puts all eukaryotic species at 8.7 million total , which implies animals make up the vast majority of that number.

What that means

  • Known species: about 1.7 million animal species have been formally described.
  • Estimated total species: around 7.7 million animal species may exist overall.
  • Uncertainty: these are estimates, not a census, so the real number could be higher or lower.

Simple way to think about it

If you imagine a giant library, scientists have cataloged a lot of the books, but many more are still undiscovered in remote habitats, deep oceans, and insect-rich ecosystems.

Bottom line

A solid quick answer is: about 7.7 million animal species are estimated to exist in the world, and about 1.7 million have been identified so far.