The Investiture Controversy or Investiture Contest is the most significant conflict between Church and state in medieval Europe.

In the 11th and 12th centuries, a series of Popes challenge the authority of European monarchies over control of appointments, or investitures, of church officials such as bishops and abbots.The investiture controversy begins as a power struggle between Pope Gregory VII (1072-1085) and Henry IV, Holy Roman Emperor (1056–1106).

A brief but significant struggle over investiture also occurs between Henry I of England and Pope Paschal II in the years 1103 to 1107, and the issue plays a minor role in the struggles between church and state in France as well.

The entire controversy is finally resolved by the Concordat of Worms in 1122.By undercutting the Imperial power established by the Salian emperors, the controversy leads to nearly 50 years of civil war in Germany, and the triumph of the great dukes and abbots, until Imperial power is reestablished under the Hohenstaufen dynasty.