We conducted a comprehensive systematic revision of deep-sea Trachyleberididae, Thaerocytheridae, and Hemicytheridae (Ostracoda, Crustacea) covering almost all Cenozoic genera using high-resolution scanning electron microscopy. Trachyleberididae, our main focus, is one of the most diverse and abundant ostracod families, but its genus-level taxonomy is still confusing. Approximately 700 specimens from 177 species from 47 genera were examined. The studied samples range in age from the Cretaceous to the present day and cover all major oceans in the world, including the Atlantic, Pacific, Indian, and Southern Oceans, the Mediterranean Sea, and the Gulf of Mexico. Five new genera and 45 new species are described: Bensonodutoitella gen. nov., Hornibrookoleberis gen. nov., Croninocythereis gen. nov., Bensonocosta gen. nov., Ryugucivis gen. nov., Abyssocythere scotti sp. nov., Ambocythere tomocaudata sp. nov., Ambocythere whatleyi sp. nov., Ambocythere hyakunome sp. nov., Atlanticythere bensoni sp. nov., Atlanticythere oculi sp. nov., Dutoitella cronini sp. nov., Dutoitella symmetrica sp. nov., Dutoitella mazziniae sp. nov., Dutoitella paradinglei sp. nov., Dutoitella ayressi sp. nov., Dutoitella colesi sp. nov., Dutoitella spinosa sp. nov., Dutoitella whatleyi sp. nov., Dutoitella atlantiformis sp. nov., Bensonodutoitella bicornigeri sp. nov., Oligocythereis sylvesterbradleyi sp. nov., Cythereis guerneti sp. nov., Cythereis johnnealei sp. nov., Cythereis parajohnnealei sp. nov., Cythereis neoanteplana sp. nov., Cythereis sylvesterbradleyi sp. nov., Cythereis bensoni sp. nov., Cythereis purii sp. nov., Cythereis fungina sp. nov., Cythereis tomcronini sp. nov., Cythereis legitimoformis sp. nov., Cythereis richardbensoni sp. nov., Cythereis dinglei sp. nov., Cythereis ovi sp. nov., Cythereis swansoni sp. nov., Croninocythereis tridentiferi sp. nov., Croninocythereis cronini sp. nov., Bensonocosta bensoni sp. nov., Ayressoleberis colesi sp. nov., Leguminocythereis? buzasi sp. nov., Legitimocythere tomi sp. nov., Ryugucivis jablonskii sp. nov., Ryugucivis acuminata sp. nov., Ryugucivis obtusa sp. nov., Phacorhabdotus mazzinireticulatus sp. nov., Phacorhabdotus nudus sp. nov., Phacorhabdotus slipperi sp. nov., Taracythere ayressoabyssora sp. nov., and Taracythere thalassoformis sp. nov. Emended concepts are proposed for several important genera to better stabilize their taxonomy. This study considerably reduces taxonomic uncertainty of this important component of the modern and fossil deep-sea ostracod community and provides a robust taxonomic baseline for deep-sea ostracod-based paleoceanographic, paleoecological, and macroevolutionary research. KEY WORDS: Deep sea, Ostracoda, taxonomy, Trachyleberididae, Thaerocytheridae, Hemicytheridae.