Chaka (Bulgarian: Чака) reigned as emperor (tsar) of Bulgaria from 1299 to 1300. The date of his birth is unknown.
Chaka was the son of the Mongol leader Nogai Khan by a wife named Alaka. Sometime after 1285 Chaka married a daughter of George Terter I of Bulgaria, named Elena. In the late 1290s, Chaka supported his father Nogai in a war against the legitimate khan of the Golden Horde Toqta, but Toqta was victorious and defeated and killed Nogai in 1299.
At about the same time Chaka had led his supporters into Bulgaria, intimidated the regency for Ivan II into fleeing the capital, and imposed himself as ruler in Tărnovo in 1299. It is not completely certain whether he reigned as Emperor of Bulgaria or simply acted as the overlord of his brother-in-law Theodore Svetoslav. He is accepted as a ruler of Bulgaria by Bulgarian historiography.
Chaka did not long enjoy his new position of power, as the armies of Toqta followed him into Bulgaria and besieged Tărnovo. Theodore Svetoslav, who had been instrumental in assisting Chaka's seizure of power, organized a plot in which Chaka was deposed and strangled in prison in 1300. His head was sent to Toqta, which in turn secured Theodore Svetoslav's position as the new emperor of Bulgaria. It seems that Theodore Svetoslav's cooperation contributed to the withdrawal of Mongol interference in Bulgaria.