Leszek of Inowrocław (pl: Leszek inowrocławski; 1275/76 – after 27 April 1339), was a Polish prince member of the House of Piast, Duke of Inowrocław during 1287-1314 (under the regency of his mother until 1294), Duke of Pomerelia (Gdańsk Pomerania) in 1296, ruler over Wyszogród since 1296, in 1300 paid homage to King Wenceslaus II of Bohemia, in 1303 sold to the Teutonic Order the Michałów Land, during 1303-1312 in captivity in Bohemia, since 1312 vassal of the Kingdom of Poland, during 1314-1320/24 sole ruler over Inowrocław, abdicated.
He was the eldest son of Ziemomysł of Inowrocław and Salome, daughter of Sambor II, Duke of Pomerelia.
After the death of their father in 1287, Leszek and his younger brothers Przemysł and Casimir III inherited his domains; however, because they are minors, remained under the regency of their mother and paternal half-uncle Władysław I the Elbow-high until 1294, when Leszek, as the oldest brother, attained his majority and assumed the government and the guardianship of his brothers. He received a good education (contemporary sources even refers to him as litteratus).
In 1296, using the confusion followed the death of Przemysł II he managed to claim the Duchy of Pomerelia, under the pretext of being a maternal descendant of the Samborides; however, shortly he was forced to resign the Duchy to Władysław I, who gave him in compensation the castellany of Wyszogród.
In 1300, after the pressure of King Wenceslaus II of Bohemia (recently crowned King of Poland), he paid homage to him. In 1303 Leszek was involved in a military conflict with his uncle Siemowit of Dobrzyń; this prolonged fight caused financial difficulties to the Duke of Inowrocław, and forced him to pledge the Michałów Land to the Teutonic Order. Soon after, and for unknown reasons, he went to Hungary to be reunited with his uncle Władysław I; because he had to pass for areas controlled by Wenceslaus II, he was captured and imprisoned, sent to Bohemia. His captivity lasted until 1312.