Michael Phelps has served as the global ambassador for Colgate's 'Save Water' initiative since 2017, encouraging consumers to conserve water by turning off the tap while brushing their teeth.

Michael Phelps has been an ambassador for Under Armour since 2010, having signed a multiyear endorsement deal with the Baltimore-based apparel brand. He endorses their products for both his training and athletic pursuits outside the pool, appearing in various campaigns and advertisements for the brand.

Michael Phelps formed a long-term strategic partnership with Aqua Sphere in 2014 to develop a global swim brand, focusing on innovative products for swimmers of all levels.

Michael Phelps partnered with Purina Pro Plan in 2024 to launch the 'Fueled By' docuseries. This series highlights the commitment of athletes to their sports and emphasizes the vital role of nutrition in enhancing active lifestyles for both them and their dogs.