A revision of the hydrophilid genus Hydrochara Berth. (Coleoptera) is presented including a historical review, a discussion of diagnostic characters and techniques, and a discussion of the phylogeny and zoogeography of this genus.Twenty-one species are recognized. Six species are described as new. H. grandis (Zimm.) is listed as species dubia. H. scrobiculata (Panzer, 1799), H. substriata (Sturm, 1843), H. intermedia (Mulsant, 1844), H. subaenea (Motschulsky, 1845), H. smaragdina (Bach, 1856), H. costata (Lüderwaldt, 1897), H. flaviventris (Ochs, 1923), and H. carinata (Jander, 1927) are placed in synonymy with H. caraboides (Linné, 1758); H. roubali (Vávra, 1923) with H. flavipes (Stev.); H. uniformis (Fairmaire, 1869) with H. elliptica (Fabricius, 1801).Neotype is designated for H. obtusata (Say). Lectotypes are designated for H. dichroma (Fairm.), H. sarta (Sem.), H. libera (Sharp), H. semenovi (Zaits.), H. profanifuga (Sem.), H. affinis (Sharp), H. uniformis (Fairm.), H. fulvofemorata (Fairm.), and H. glauca (LeC.).Key to species is provided, each species is described and illustrated, and all available bionomic and distributional data are presented; distributional records are mapped.