Ratzeburg is a town in Schleswig-Holstein, Germany. It is situated in the middle of four lakes, that leave just narrow access paths to the town. Ratzeburg is the capital of the Kreis (district) of Lauenburg. Population 12,300 (1999).

The town was founded in the 11th century. The name is believed to be derived from the local Slavic ruler Ratibor, who was nicknamed Ratse. In the year 1044 Christian missionaries under the leadership of the monk Ansverus came into the region and built a monastery. It was destroyed in a pagan rebellion in 1066, the monks were stoned to death. Today monuments to the missionaries in two of the town's churches commemmorate these events. Ansverus was later sainted, his bones were entombed in the Ratzeburg cathedral.

Henry the Lion became the ruler of the town in 1143 and established a bishopric in 1154. Later the city became part of the duchy of Sachsen-Lauenburg. The cathedral and its surroundings, however, became part of the duchy of Mecklenburg-Strelitz from 1648 to 1937. The town was almost completely destroyed in 1693, when Christian V of Denmark shot Ratzeburg to ashes. After this event it was rebuilt in Baroque style.