Since October 2016, 10 ground-based stations have been progressively equipped for continuous measurements of UV indices and atmospheric cloud fraction. All these instruments form the UV-Indien measurement network. The stations are homogeneously distributed in 5 countries of the Western Indian Ocean region (Comoros, France, Madagascar, Mauritius and Seychelles). The main scientific objectives of this network are to study the annual and inter-annual variability of the ultraviolet (UV) radiation in this area, to validate the output of numerical models and satellite estimates of ground-based UV measurements, and to monitor UV radiation in the context of climate change and projected ozone depletion in this region. This study presents the measurements of 4 stations of the UV-Indien network, carried out since the end of 2016 for some of them: - the Antananarivo - Madagascar station is a tropical urban site of altitude (18.92° S, 47.56° E, 1300 m), - the station of St Denis/La Réunion (20.9° S, 55.5° E, 85 m) is a coastal urban site on a mountainous sub-tropical island - the station of Mahé - Seychelles is an equatorial coastal urban site (4.61° S, 55.45° E, 50 m), - the station of Rodrigues Island - Mauritius is a tropical coastal rural site (19.76°S, 63.37°E, 60 m). These measurement sites correspond to various and particular environments (mountain, maritime, rural, urban) and to various latitudes (equatorial, tropical and sub-tropical). In this region, the average UVI measurements are extreme and above 11 for most of the year. The mean climatological UVI values at local solar noon range between 10 UVI units (Antananarivo, Rodrigues and Saint-Denis) and more than 14 UVI units at Mahé. However, the observed maxima (for all-sky conditions) are much higher and can reach more than 20 UVI in Mahé in summer. [ABSTRACT FROM AUTHOR]