The Southeast Asian whirligig beetle genus Porrorhynchus Laporte, 1835 is revised. The genus is composed of five species, P. depressus Régimbart, 1892, P. indicans (Walker, 1858), P. landaisi Régimbart, 1892, P. marginatus Laporte, 1835, and P. misoolensis (Ochs, 1955), new status, and two subgenera, Porrorhynchus s. str. and Rhomborhynchus Ochs, 1926. The characters uniting the species within the two subgenera are discussed, as is their relation to the genus Dineutus Macleay, 1825. New synonyms are established: Ceylorhynchus Brinck, 1955 is synonymized with the Porrorhynchus s. str.; P. barthelemyi Régimbart, 1907 and P. landaisi latilimbus Ochs, 1926 are synonymized with P. landaisi; P. marginatus mjobergi Ochs, 1926 is synonymized with P. marginatus; Dineutus (Rhomborhynchus) depressus jamurensis Ochs, 1955, Dineutus (Rhomborhynchus) depressus versteegi Ochs, 1955, and Dineutus (Rhomborhynchus) depressus moszkowskii Ochs, 1955, are synonymized with P. (Rhomborhynchus) depressus. Porrorhynchus misoolensis (Ochs, 1955) is elevated to full species status. Lectotypes are designated for P. brevirostris Régimbart, 1877, P. tenuirostris Régimbart, 1877, P. landaisi Régimbart, 1892, P. barthelemyi Régimbart, 1907, P. marginatus mjobergi Ochs, 1926, and P. landaisi latilimbus Ochs, 1926. Each species has its dorsal habitus imaged, male and female genitalia illustrated, important morphology illustrated, complete catalog of associated names and their use, distribution mapped, and proposed common name proposed, along with a discussion section. A key to the species is included, as is a checklist of the species that includes synonyms and common names.