Hello World is a live show in which the UK's biggest YouTube stars perform for and meet with their fans on 28 and 29 October.
Zoe Sugg started her blog and YouTube channel in 2009 and now has more than 12 million subscribers to her main channel where she talks beauty, fashion and life in general. She's followed her online success with massive sales of a series of young adult novels.
Alfie Deyes talks lifestyle, technology and gaming across three YouTube channels. He's also Zoella's other half.
Among other things, Caspar Lee interviews big-name celebrities and hangs out with other YouTubers Joe Sugg and Alfie Deyes. He was also seen in the video for Charlie XCX song "Boys".
Rose Dix and Rosie Spaughton are a married comedy duo who specialise in improv, and also run a gaming channel.
A friend of Caspar Lee since their schooldays in South Africa, Josh Pieters plays sketches and pranks on his channel and in Snapchat videos fro Comedy Central.
Specialising in covers on their YouTube channel, New Hope Club are a pop trio signed to a record deal by popular group The Vamps.
4.5 million fans watch Marcus Butler's comedy channel. You might also have seen him on 2016's "Celebrity MasterChef".