Constantine II (Bulgarian: Константин, romanized: Konstantin) ruled as emperor (tsar) of Bulgaria in Vidin from 1397 to 1422.

At that time, Ivan Stratsimir was contributing with soldiers to assist the Christian nations' bid to resist the advance of the Ottoman Empire.

[1][2] Some Bulgarian historians suppose that Tsardom of Vidin's most western territories may have remained under Constantine II's rule almost until his death in 1422.

The anti-Ottoman rebellion lasted for half a decade (1408–1413) and spread to much of Bulgaria until the rebels were defeated by the Ottoman Sultan Musa.

The Bulgarians attempted to make up for their losses by siding with Musa's brother and rival Sultan Mehmed I, but the latter's victory did little to improve their situation.