The hydrophiloid beetles (Georissidae, Hydrophilidae) of Socotra Island (Yemen) are reviewed based mainly on the material collected during the Czech expeditions undertaken between 2000 and 2012. A total of 16 species are recorded, three of which are newly described herein: Georissus (Neogeorissus) maritimus sp. nov., G. (N.) nemo sp. nov. (Georissidae) and Hemisphaera socotrana sp. nov. (Hydrophilidae).
Seven species are recorded from Socotra Island for the first time: Georissus (Neogeorissus) sp., Berosus corrugatus Regimbart, 1906, Laccobius eximius Kuwert, 1890, L. minor (Wollaston, 1867), L. praecipuus Kuwert, 1890, Enochrus nitidulus (Kuwert, 1888), and Sternolophus unicolor Laporte de Castelnau, 1840. The previously published Socotran record of Sternolophus decens Zaitzev, 1909 is considered as misidentification.
The Socotran hydrophiloid fauna is found to consist mostly of widely distributed African, Arabian/Near Eastern, Oriental and cosmopolitan species. The three newly described species may be considered as endemic to Socotra, but two of them seem to have close relatives in Africa and southern India.
Notes on the remaining described species of the genus Hemisphaera Pandelle, 1876 are also included.