The Ninetieth Wisconsin Legislature convened from January 7, 1991, to January 4, 1993, in regular session, and also convened in five special sessions.

[1] Senators representing odd-numbered districts were newly elected for this session and were serving the first two years of a four-year term.

Assembly members were elected to a two-year term.

Senators representing even-numbered districts were serving the third and fourth year of a four-year term, having been elected in the general election of November 8, 1988.

[1] The governor of Wisconsin during this entire term was Republican Tommy Thompson, of Juneau County, serving the first two years of his second four-year term, having won re-election in the 1990 Wisconsin gubernatorial election.