Saber-tooth cats is the informal name for Machairodontinae, an extinct subfamily of carnivoran mammals of the family Felidae (true cats). They were found in Asia, Africa, North America, South America, and Europe from the Miocene to the Pleistocene, living from about 16 million until about 11,000 years ago. The name means "dagger-tooth", from Greek μάχαιρα (machaira), sword.
The Machairodontinae contains the genus Smilodon (arguably the "prototype" for the popular image of the saber-toothed cat), as well as other cats with only minor increases in the size and length of their maxillary canines. Sometimes, other carnivorous mammals with elongated teeth are also called saber-toothed cats, although they do not belong to the felids.
In the works of Harry Turtledove, "saber-toothed cat" or "saber-tooth tiger" usually refers to Smilodon, which was native to the Americas. This page should include saber-toothed cats that are native to Eurasia and Africa, or are fantasy analogs.