Bulgaria has been a traditionally Christian state since adopting Christianity as the state religion in 865.

An excerpt from the article 34 facts about Bulgaria

The dominant denomination is the Bulgarian Orthodox Church. More than 60% of the country's population professes Christianity. Catholicism came to Bulgaria in the Middle Ages, and Protestantism in the 19th century. According to the 2011 census, the total number of Catholics in the country was approximately 49.000, and over 64.000 were Protestants. The majority of Roman Catholic inhabitants live in Plovdiv, as well as in some villages in northern Bulgaria. There is also a large Muslim minority in Bulgaria, numbering approximately 580.000 believers, most of whom are Turks - Islam has its origins in Bulgaria in the 9th century.