Abel of Denmark (1218-1252), was Duke of Schleswig 1232-1252 and King of Denmark from 1250 until his death. He was the son of Valdemar II by his wife, princess Berengaria of Portugal and succeeded to the throne on November 1, 1250, after the death of his brother Eric IV of Denmark. Eric IV was apparently slain by two of Abel's men after a year-long conflict between the two brothers, and even though Abel and twenty-four noblemen swore an official oath ("dual dozen's oath", in Danish "dobbelt tylvter-ed") that the Duke had no part in the killing, it was (and is) widely believed that King Eric was killed at his brother's bidding. "Abel by name, Cain by his deeds" ("Abel af navn, Kain af gavn"), or so people said.

Abel and Queen Mechtildis only ruled for a year and a half, however, before Abel was killed in battle on June 29, 1252. His half-grown son Valdemar was held for ransom by the Archbishop of Cologne at the time, and so it was Eric and Abel's youngest brother Christopher I who was crowned King on Christmas day 1252.