The Tiasmyn (Ukrainian: Тясмин) is a right tributary of the Dnieper River in Ukraine.

Along the river's lower section there are important discovery sites of the Bilogrudivka/Chernoles culture near the settlement of Subotiv.

These findings represent key late Bronze Age discoveries.

Cities and towns located on the river include: Kamianka, Smila, and Chyhyryn.

This article related to a river in Ukraine is a stub.