Kaloyan or Kalojan (), also known by his Vlach name Johannitsa or Ioannitsa ( 1170 – October 1207), was Tsar of Bulgaria from 1196 to 1207. He was a younger brother of Theodor and Asen who led the anti-Byzantine uprising of the Bulgarians and Vlachs (proto-Romanians of the Balkans) in 1185. The uprising ended with the restoration of the independence of Bulgaria. He spent years as a hostage in Constantinople in the late 1180s. Theodor (who had been crowned emperor under the name Peter) made him his co-ruler after Asen was murdered in 1196. A year later, Theodor-Peter was also assassinated, and Kaloyan became the sole ruler of Bulgaria.