Ravensberg

The Counts of Ravensberg, of the House of Calvelage-Ravensberg, ruled a county in eastern Westphalia at the foot of the Teutoburg Forest, first attested in the twelfth century. Their original seat was Ravensberg Castle; around 1240 to 1250 Otto III built Sparrenberg Castle above Bielefeld and moved there.

Otto III's daughter Adelaide married Landgrave Otto I of Hesse in 1297, and his son Otto IV's daughter Hedwig wed Duke William II of Brunswick-Lüneburg. Otto IV died in 1328 leaving only daughters; his brother Bernard ruled until his death without issue in 1346.

The county passed to Gerhard VI of Jülich, husband of Otto IV's daughter Margaret, and was united with Berg in 1348. The Treaty of Xanten awarded Ravensberg to Brandenburg in 1614, which administered it with Minden until the county's dissolution in 1807.