The Eighty-Ninth Wisconsin Legislature convened from January 3, 1989, to January 7, 1991, in regular session, and also convened in two special sessions.

[1] Senators representing even-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 odd-numbered districts were serving the third and fourth year of a four-year term, having been elected in the general election of November 4, 1986.

[1] The governor of Wisconsin during this entire term was Republican Tommy Thompson, of Juneau County, serving the second two years of a four-year term, having won election in the 1986 Wisconsin gubernatorial election.