Tux is a penguin made with The Gimp by Larry Ewing. The concept of the Linux mascot being a penguin came from Linus Torvalds, the creator of Linux. Tux was created by Larry Ewing in 1996 after an initial suggestion made by Alan Cox and further refined by Linus Torvalds on the Linux kernel mailing list. The first person to call the penguin "Tux" was James Hughes who said that it stood for "(T)orvalds (U)ni(X)".

Tux was designed for a Linux logo contest. Confusingly, there were actually three separate contests and Tux didn't win any of them. This is why Tux is formally known as the Linux mascot and not the logo. According to Jeff Ayers, Linus Torvalds had a "fixation for flightless, fat waterfowl" and Torvalds claims to have contracted "penguinitis" after being gently nibbled by a penguin: "Penguinitis makes you stay awake at nights just thinking about penguins and feeling great love towards them." Torvalds' supposed illness is of course a joke, but he really was bitten by a Little Penguin on a visit to Canberra, Australia. Torvalds was looking for something fun and sympathetic to associate with Linux, and a slightly fat penguin sitting down after having had a great meal perfectly fit the bill.

Tux has become iconic for Linux, with one British Linux user group adopting a live Black-Footed (Jackass) penguin at Bristol Zoo on the occasion of Linus Torvalds' birthday.