Sweyn III of Denmark

Sweyn III Grathe (c. 1125–1157) was the illegitimate son of Eric II the Memorable. When Eric III abdicated in 1146, Zealand's magnates elected Sweyn king while Jutland's crowned Canute V, opening a civil war. Sweyn held on through shifting alliances with Canute V and his cousin Valdemar.

In 1157 the three agreed to partition Denmark, but at a banquet in Roskilde Sweyn's men murdered Canute V while Valdemar escaped. Valdemar raised an army and defeated Sweyn at the Battle of Grathe Heath in 1157, and Sweyn was killed after it.