Flutter will partner with the 2023, 2024 and 2025 editions of the event, each aiming to raise £1m for the charity.
The Tour 21 features a team of 20 amateur cyclists completing all 21 stages of the Tour de France professional cycling race.
The 2023 event will cover 3,000km and take place from 24 June to 16 July.
All funds raised are invested into the Trials Acceleration Programme (TAP) network, benefiting over 20 million people with access to specialized treatments for blood cancer not available through standard care.
The funding of over £1m each year facilitates the treatments for blood cancer through a team of specialist research nurses and other clinical roles.
Flutter’s group head of communities, Kerry McNally, said, “It is an exciting partnership that combines our passion for sport with our commitment to social responsibility, supporting the communities in which we operate.”
Cure Leukaemia’s chief executive, James McLaughlin, added, “Flutter’s headline partnership takes The Tour 21 to a whole new level, significantly boosting the event’s fundraising total and global impact.”