Tomislav (died 928) is a ruler of Croatia in the Middle Ages.

He reigns from 910 until 928, first as Duke (dux Croatorum) of Dalmatian Croatia in 910–925, and then becomes first King (rex Croatorum) of the Croatian Kingdom in 925–928.

Tomislav wis one of the most prominent members of the House of Trpimirović.

He unites the Croats of Dalmatia and the Slavs of Pannonia into a single state and is generally credited as the founder of a kingdom which lasts for several centuries.

He is said to have ruled over the territory of today's Croatia and Bosnia, rounding off his state from the Adriatic Sea to the Drava river, and from the Raša river in Istria to the Drina river.

Since the historical records of him are scarce, it is assumed that he was the son of Muncimir, Duke of Dalmatian Croatia, whom he succeeded around 910.