The Serbian Empire was a medieval Serbian state that emerged from the Kingdom of Serbia. It was established in 1346 by Dušan the Mighty, who significantly expanded the state.

Simeon Uroš, nicknamed Siniša (Синиша), was a self-proclaimed Emperor of Serbs and Greeks, from 1356 to 1370. He was son of Serbian King Stephen Uroš III and Byzantine Princess Maria Palaiologina. Initially, he was awarded the title of despot in 1346, and appointed governor of southern Epirus and Acarnania in 1347 by his half-brother, Serbian Emperor Stephen Dušan. After Dušan's death in 1355, the Serbian throne passed to Dušan's son Stephen Uroš V, but despot Simeon decided to seize the opportunity in order to impose himself as co-ruler and lord of all southern provinces of the Serbian Empire. That led him to conflict with his nephew in 1356, when Simeon started to expand his control in southern regions of the Empire, trying to take Thessaly and Macedonia. He proclaimed himself Emperor of the Serbs and Greeks, creating a separate state, centered in regions of Thessaly and Epirus, where he ruled until his death in 1370. He was succeeded by his son Jovan Uroš.