Wartislaw I (Warcisław I) (around 1092 – died August 9, 1135) was the first historical ruler of the Duchy of Pomerania and the founder of the Griffin dynasty. Most of the information about him comes from the writings on the life of Otto of Bamberg. He was of Slavic origin, most likely born around the turn of the twelfth century. Early in life he was probably a "crypto-Christian", after being baptized while a prisoner of the Saxons, because he wanted to hide his new religion from his still pagan subjects. In 1109 Wartislaw was defeated in the Battle of Nakło by Bolesław III Wrymouth, the Duke of Poland, to whom he became a vassal sometime between 1120 and 1123. He agreed to pay tribute to Bolesław, as well as to Christianize Pomerania. To that effect, he, along with Bolesław, backed Otto of