Simeon Uroš Nemanjić, nicknamed Siniša, also known in Greek as Symeōn Ouresēs Palaiologos, is the Tsar of Epirus from 1359 to 1366, and of Thessaly from 1359 until his death in 1370.

He governs Epirus and Acarnania under his half-brother Emperor Stephen Uroš IV Dušan of Serbia (r. 1331-1355) from 1348.

After Stephen's death in 1355, Simeon rules these regions as self-proclaimed Emperor of the Serbs and Greeks in rivalry with his nephew Stephen Uroš V of Serbia.