We report the aquatic Coleoptera (families Dryopidae, Dytiscidae, Georissidae, Gyrinidae, Heteroceridae, Hydraenidae, Hydrophilidae and Limnichidae) from North Oman, mostly based on the captures of fourteen localities sampled by the authors in 2010. Four species are described as new, all from the Al Hajar mountains, three in family Hydraenidae, Hydraena (Hydraena) naja sp. nov., Ochthebius (Ochthebius) alhajarensis sp. nov. (O. punc-tatus species group) and O. (O.) bernard sp. nov. (O. metallescens species group); and one in family Hydrophilidae, Agraphydrus elongatus sp. nov. Three of the recorded species are new to the Arabian Peninsula, Hydroglyphus farquharensis (Scott, 1912) (Dytiscidae), Hydraena (Hydraenopsis) quadricollis Wollaston, 1864 (Hydraenidae) and Enochrus (Lumetus) cf. quadrinotatus (Guillebeau, 1896) (Hydrophilidae). Ten species already known from the Arabian Peninsula are newly recorded from Oman: Cybister tripunctatus lateralis (Fabricius, 1798) (Dytiscidae), Hydraena (Hydraena) gattolliati Jäch & Delgado, 2010, Ochthebius (Ochthebius) monseti Jäch & Delgado 2010, Ochthebius (Ochthebius) wurayah Jäch & Delgado, 2010 (all Hydraenidae), Georissus (Neogeorissus) chameleo Fikáček & Trávníček, 2009 (Georissidae), Enochrus (Methydrus) cf. tetraspilus Régimbart, 1903, Laccobius (Hydroxenus) leucaspis Kiesenwetter, 1870, Paracymus relaxus Rey, 1884 (all Hydrophilidae), Dryops lutulentus (Erichson, 1947) (Dryopidae), and Augyles flavidus (Rossi, 1794) (Heteroceridae). A total of 73 species of aquatic Coleoptera are presently known from Oman, although this number is expected to increase substantially with further sampling. A checklist of the species of aquatic Coleoptera from the Arabian Peninsula is provided.