Przemysl Ier de Grande Poland (in Polish Przemysł I Wielkopolski ), from the dynasty of the Piasts, was born between the June 5th 1220 and the June 4th 1221, and deceased with Poznań the June 4th 1257. He is the oldest son of Ladislas Odonic and Hedwige.

He was Duc Ujście (1239 - 1241), duke of Large-Poland with his brother (1241 - 1247), duke of Kalisz (starting from 1244), duke of Poznań and Gniezno (1247 - 1249), duke of Ruda (starting from 1249), duke of Poznań and Kalisz (1249 - 1250), duke of all Large Poland (1250 - 1253) and duke of Poznań (1253 - 1257).

In 1239, with died of his/her father, it inherits the part of Large Poland that Ladislas Odonic controlled and becomes duke of Ujście. It will endeavor to recover all the territories of Large Poland. In 1241, after the death of Henri II the Piles with the Battle of Legnica, Przemysl and his/her brother Boleslas the Piles seize the areas of Poznań and Gniezno. On their impetus, they seize all the towns of Large Poland which were controlled by the Silesia. In 1244, it marries Elisabeth, a girl of Henri II the Piles. In exchange, Przemysl obtains Ladislas d' Opole the return of the area of Kalisz in the duchy of Large Poland. In 1247, Przemysl becomes duke of Poznań and of Gniezno and, under the pressure of the Noblesse, must leave the duchy of Kalisz to his/her brother. He also obtains Santok Boleslas II the Bald person. He is combined with Bogufał II, the bishop of Poznań. In 1249, it makes an exchange with his/her brother and becomes duke of Poznań and Kalisz. In 1250, for reasons which are unknown for us, it imprisons his/her brother and becomes duke of all Large Poland (Poznań, Gniezno and Kalisz) until in 1253. In 1253, it releases his/her brother and leaves him Kalisz and Gniezno, preserving Poznań. It gives the Droit of Magdeburg to this city. The May 8th 1254, in Cracow, in company of others Piasts (in particular Boleslas Piles, Casimir Ier de Cujavie, Siemovit Ier de Mazovie, Ladislas d' Opole and Boleslas V Modest the), it takes part in the ceremonies celebrating the Canonization Saint Stanislas.

One of the big problems to which it has to face during all its reign is the expansion policy of the Brandebourg. Without much of success, it tried to establish relations of good neighborhood.

Przemysl Ier de Grande Poland dies with Poznań the June 4th 1257. He is the father of four girls and a son (Przemysl II).