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Little is known about microplastics (MPs) in corals from the Indian Ocean. We compared MP concentrations, morphotypes, size, colours, and polymer compositions in six coral genera from three remote Mascarene islands (Rodrigues, St. Brandon's Atoll, and Agalega) of the Republic of Mauritius, on a 1200 km transect located in the South Equatorial Current (SEC). The mean MP concentration was 0.78 n/g (53 % fibres) with no significant differences between islands. Polymers were polypropylene (78 %) and polyethylene (18 %). We conclude that the SEC's MP concentrations and compositions have homogenized over thousands of kilometres across the Indian Ocean. We discuss the lack of hazardous polyurethane MPs in coral samples given obvious sources on St Brandon. To the best of our knowledge, this study is the first to report on MPs in coral from the Western Indian Ocean and the Mascarene Islands providing a baseline for further research, monitoring, mitigation, and policy development. [Display omitted] • Nothing is known about microplastics (MPs) in coral from the Western Indian Ocean. • We analysed MPs from hard and soft corals from three Mascarene islands, a 1200 km transect. • The mean concentration was 0.78 n/g (53 % fibres) with no significant differences between islands. • Polymers were polypropylene (78 %) and polyethylene (18 %). • Compositions homogenized over thousands of kilometres across the Indian Ocean. [ABSTRACT FROM AUTHOR]