Thomas & Friends is a British children's television series which aired from 9 October 1984 to 20 January 2021. Based on The Railway Series books by Wilbert Awdry and his son Christopher, the series was developed for television by Britt Allcroft. The series follows the adventures of Thomas the Tank Engine—an anthropomorphic blue steam locomotive who lives on the fictional Island of Sodor—as well as his various friends. Initially being filmed in live action on model sets, whereas the latter half of its run was produced using CGI, over 500 episodes were produced over the course of 24 series.

In the United States, it was first broadcast along with the spin-off series, Shining Time Station, on PBS' PTV Park block on 29 January 1989, while broadcast of the series did shift over time, it later aired on PBS Kids up until 2017. The rights to the series are currently owned by HIT Entertainment (a subsidiary of Mattel), which acquired Gullane Entertainment in July 2002. HIT was folded into Mattel in 2016.

An American 2D animated reboot, Thomas & Friends: All Engines Go, premiered on 13 September 2021 on Cartoon Network's preschool block Cartoonito.