Eric I, Duke of Schleswig

The seal of Eric I, the first known example of the coat of arms of Schleswig.

Eric I Abelsøn (died 27 May 1272) was a Danish nobleman. He was the ruling Duke of Schleswig from 1260 until his death in 1272. He was the second son of King Abel of Denmark, Duke of Schleswig and Mechtild of Holstein.

Early life Eric was born in . After the death of his elder brother Duke Valdemar III in 1257, Eric inherited the claim to the Duchy of Schleswig. However, his uncle and potential feudal overlord King Christopher I of Denmark refused to install him as duke.

Marriage and issue Eric married Margaret of Rugia, a daughter of Jaromar II, Prince of Rugia in 1259. They had the following children:

Margaret (died after 1313), married Helmold III, Count of Schwerin Valdemar IV, Duke of Schleswig Eric (Longbone), from 1295 Lord of Langeland (1272–1310), married Sophia Burghardsdatter (died 1325), daughter of Queen dowager Jutta of Denmark and Count Burchard VIII of Querfurt-Rosenburg, Burgrave of Magdeburg