Hachirōgata or Hachirō Lagoon (八郎潟, Hachirō-gata) is a lake in Akita Prefecture in northern Japan.

Its formal name is Lake Hachirō (八郎湖, Hachirō-ko), but it is also called Hachirōgata Regulating Pond (八郎潟調整池, Hachirō-gata chōseichi).

Extensive reclamation began in 1957 for crop production, and Ōgata village was established on the reclaimed land on October 1, 1964.

Fishery of shijimi shells (Corbicula japonica) was a thriving industry, but it decreased as the lake became less brackish.

According to a legend, a man called Hachirō was transformed into a dragon and chose the lake for his home after wandering a long time.