Harry Styles has just launched onto the solo scene with his debut single, Sign the Times, but most his bandmates have come before him.
Zayn Malik was the first to release a solo single, Pillow Talk, last year, followed by Niall Horan's This Town in September.
Louis Tomlinson teamed up with Steve Aoki on the electro dance track, Just Hold On, at Christmas with Liam Payne's solo material yet to be released.
So we've worked out which One Direction member is the most successful by how many copies their solo single they sold in their first week.
Zayn - Pillow Talk - 112,497 sales
Zayn's debut solo single was released on January 26, 2016, and reached number one in its first week.
Harry Styles - Sign the Times - 62,900 sales
Harry's single was released on April 7 and debuted at number one to end Ed Sheeran's 13-week reign at the top the UK charts.
Louis Tomlinson - Just Hold On - 47,626 sales
Louis' collaboration with Steve was released on December 10 in attempt to secure a Christmas number one, but it ended up in second place behind Clean Bandit's Rockabye.
Niall Horan - This Town - 37,358
Niall released his debut single on September 29, and it entered the chart at number 100. The next week it peaked at number nine.
Liam Payne has yet to release any music - what with him becoming a dad and all - but its definitely coming this year.