The Taiseikai (Japanese: 大成会, lit. Great Achievement Society) was a political party in Japan. It was active from 1890 to 1891.
Following the July 1890 elections the Taiseikai was established by a group of 79 newly elected and pro-government National Diet members who were largely former civil servants. The second-largest party after the Rikken Jiyūtō, it was a largely pragmatic group rather than adhering to certain principles.
The party split in November 1891 over its support for the government, with a group breaking away to form the Tomoe Club, and it ceased to exist by the time of the February 1892 elections.