Casimir I (or Kasimir I) (after 1130 – 1180) was duke of Pomerania since his uncle Ratibor I's death in 1155/56.

After the lost 1164 Battle of Verchen, where Casimir and Bogislaw aided an Obodrite rebellion against the duke of Saxony, Henry the Lion, Casimir and Bogislaw joined Saxony receiving their respective part duchies as a fief from Henry the Lion.

When Saxony allied with the Danes to subdue the Rani kingdom of Rügen in 1168, Casimir as well as Bogislaw aided Henry.

Casimir participated in other campaigns launched by Henry the Lion, as an 1178/79/80 expedition into Lusatia and Jüterbog.

He participated in founding the monastery Dargun (1172/74) and in 1176/80 granted privileges to the bishopric of Wollin that moved its seat to Cammin (now Kamień Pomorski) because of Danish expeditions.