Louis Tomlinson was born on December 24, 1991, in the town of Doncaster in South Yorkshire, England. His parents, Johannah and Troy Austin, divorced when he was young, and he took his stepfather Mark Tomlinson's last name as his own. Tomlinson grew up with five half-sisters: Georgia, Charlotte, Félicité and twins Daisy and Phoebe. His mother and stepfather later divorced. In 2014, Tomlinson's family expanded again as his mother welcomed another set of twins, Ernest and Doris, with husband Daniel Deakin.

When Tomlinson's baby twin sisters had minor roles on the television comedy Fat Friends, Louis went along and was also cast as an extra. Tomlinson, then 11 years old, took acting lessons and went on to receive small parts on the television dramas If I Had You and Waterloo Road.

In Doncaster, Tomlinson attended The Hayfield School; when he failed to graduate, he completed his studies at Hall Cross Academy. At Hall Cross, he performed in several school productions, including the musical Grease. Outside school, he worked part-time jobs in retail and at the Doncaster Rovers Football Club.

Tomlinson auditioned for the television talent competition The X Factor in 2009 but was turned down. However, when he returned to try out for the show's seventh season in 2010, his rendition of the song "Hey There Delilah" by the Plain White T's brought him successfully into the competition. He advanced several rounds, singing hits like Adele's "Make You Feel My Love." He was eliminated before the final round, but the judges united him with his fellow competitors Styles, Horan, Payne and Malik to form a group act. This new band, called One Direction, finished the competition in third place and received a contract with Simon Cowell's music label.
In later years, after his success with One Direction, Tomlinson returned to The X Factor as a judge and mentor. In late 2018, one of his protégés, Jamaican singer Dalton Harris, won season 15 of the show.

Tomlinson enjoyed worldwide success as part of One Direction. The band's first single, "What Makes You Beautiful," was released in September 2011 in the United Kingdom and became a global No. 1 hit. Their first album, Up All Night, was released in early 2012 and was a chart-topper in 16 countries; their second album, Take Me Home (2012), was also a hit. One Direction performed at the 2012 Summer Olympics closing ceremony in London and has toured the world.

One Direction continued to dominate the pop music scene, releasing two more successful albums. Midnight Memories debuted in 2013 and was quickly followed by 2014's Four, the group's fourth consecutive studio effort to debut at No. 1.

The group went through a major shake-up in 2015, beginning with the departure of Zayn Malik in March. But One Direction finished the year with a flourish, releasing a new album, Made in the A.M., and winning Artist of the Year at the American Music Awards. The group then made one final appearance, on Dick Clark's New Year's Rockin' Eve, before dispersing for an extended hiatus.

One Direction returned to the spotlight in February 2017, when its final single from Made in the A.M., "History," was named Video of the Year at the Brit Awards. Unable to attend the event, Tomlinson posted a clip to Twitter in which he thanked the group's fans, saying, "You continue to surprise us with just how incredible you are."

The artist's mother, Johannah, succumbed to leukemia in late 2016, at age 43. Fifteen months later, Tomlinson endured another tragedy when his 18-year-old sister, Félicité, died following a heart attack. In January 2016, Tomlinson welcomed a son, Freddie Reign, with Briana Jungwirth.