The 2005 Schleswig-Holstein state election was held on 20 February 2005 to elect the members of the Landtag of Schleswig-Holstein. The incumbent coalition government of the Social Democratic Party (SPD) and The Greens led by Minister-President Heide Simonis was defeated, bringing an end to 17 years of SPD governments in the state.

Heide Simonis was a German author and politician of the Social Democratic Party (SPD). She was minister of finance in Schleswig-Holstein from 1988 until 1993, when she became minister-president of Schleswig-Holstein. She was the first woman to serve as head of a state government in German history and the only woman to do so in the 20th century, serving until 2005. As of September 2023, she is also the longest serving former female minister-president of a German state.