Casimir II (also spelled Kasimir II) (Kazimierz II pomorski) (c. 1180 – 1219) was the duke of Pomerania-Demmin from 1187 until his death. He was succeeded by Wartislaw III, Casimir's son with princess Ingardis of Denmark.
Casimir II was the son of Bogislaw I and Anastasia, a daughter of the Polish duke Mieszko III. After his father's death in 1187, Casimir received Pomerania-Demmin as his share of the duchy of Pomerania, after his older brother Bogislaw II had received the other part duchy Pomerania-Stettin and his other older brother, Wartislaw II, who is assumed to have received Pomerania-Demmin from their uncle, Casimir I in the first place, had died in 1184.
As Casimir still was a minor in 1187, his mother Anastasia ruled in his place until 1194 as well as, until 1189, the Swantiboride Wartislaw II Swantiboritz, who was Castellan of Szczecin, and thereafter the Rugian prince Jaromar I. Despite his predecessors having joined the Holy Roman Empire in 1181, Casimir and Bogislaw II had to yield to Danish pressure put on Pomerania. Denmark had already subdued the neighboring Principality of Rügen, and Bogislaw and Casimir eventually became vassals to Canute VI of Denmark.
The Danish influenced Casimir's reign not only by appointing Jaromar, their vassal and ally, to be his legal guardian, but also by determining the northern borders of Pomerania-Demmin that were disputed by Pomerania and Rügen, with Rügen claiming the Peene river and Pomerania claiming the Ryck river further north to be the border. The decision of Canut that had to be accepted by Anastasia favoured the Rugian demands, only the trans-Peene terrae Wolgast, Lassan and Ziethen were put under Pomeranian control with the larger part of the disputed area, including the terrae Lositz (Loitz) and Wostrose (Wusterhusen), remaining within Rügen.