The Bulgarian Communist Party (BCP) (Българска Комунистическа Партия, Balgarska Komunisticheska Partiya; БКП, BKP) was the Communist and Marxist-Leninist ruling party of the People's Republic of Bulgaria from 1946 until 1989 when the country ceased to be a communist state. The Bulgarian Communist Party had dominated the Fatherland Front coalition that took power in 1944, late in World War II, after it led a coup against Bulgaria's tsarist regime in conjunction with the Red Army's crossing the border.
From 1954 until 1989 the party was led by Todor Zhivkov, who was very supportive of the Soviet Union and remained close to its leadership after Nikita Khrushchev was deposed by Leonid Brezhnev.
More information on the English [1] and Bulgarian [2] Wikipedia pages.