The 10-hour Les Mills Live London event, which will mark the beginning of the brand's global tour for 2016, is expected to attract 4,000 people.
It will see instructors host 35 different fitness classes over five stages, including new high intensity interval training (HIIT) sessions, as well as Les Mills’ signature Bodypump and Bodycombat classes.
One of the stages will include the 'sponsors' village' where Reebok is the headline sponsor.
Martin Franklin, chief executive at Les Mills UK, said: "The appointment of Itch is off the back of their experience and knowledge around creating and producing live brand experiences. We are excited about what they can bring to the Les Mills Live events, especially given their considerable experience in consumer facing sport and music festival activations."
Michael White, managing director of Itch, added: "We were incredibly excited when Les Mills asked us to join their team. There is real convergence between music, sport and the live consumer experience as a brand building opportunity, and with 14 years knowledge around establishing festival experiences as well as our recent success with Virgin Media at the Glasgow Commonwealth Games and our work with Uefa and the NFL, we are well placed to deliver a compelling proposition to clients."
Les Mills hosted a series of One Live events in partnership with Reebok last year, and the final event was held in Manchester.