Bulgaria–Russia relations (Bulgarian: Отношения между България и Русия, romanized: Otnosheniya mezhdu Bulgariya i Rusiya, Russian: Отношения между Болгарией и Россией, romanized: Otnosheniya mezhdu Bolgariey i Rossiey) are the diplomatic relations between the countries of Bulgaria and Russia.

After a Communist takeover in 1945, Bulgaria was a Soviet ally during the Cold War, and maintained good relationships with Russia until the Revolutions of 1989, the only major period since independence where Russia had better relations with Bulgaria than with Serbia; or rather in this case Tito's Yugoslavia.

With this act, Bulgaria practically Christianized and civilized the vast Slavic sea and thus annexed this space to the old Bulgarian literature and culture.

[2][3][4][5] Both nations had a tradition of calling monarchs tsars, a Slavic word for emperor that also originated in Bulgaria.

[6][7] Relations between the two started to worsen when Russia refused to diplomatically support Bulgaria in the Bulgarian unification and the following Serbo-Bulgarian War.

When Bulgaria got a chance to occupy Constantinople during the First Balkan War against the Ottoman Empire, Russia opposed Bulgarian military actions.

Eventually, Bulgaria and Russia suffered heavy military losses for their wars, and Bulgarian–Russian relations severed.

British Prime Minister Winston Churchill and Soviet First Secretary Joseph Stalin signed the secret percentages agreement at the Fourth Moscow Conference allowing the Soviet Union 80 percent of influence in Bulgaria after the war.

[14] From 1945 to 1948, the country became entrenched within the Soviet sphere of influence under the control of the Bulgarian Communist Party, which oversaw a program of Stalinization in the late 1940s and 1950s,[15] and joined the Warsaw Pact in 1955.

[15] Georgi Ivanov, a military officer from Bulgaria became the first Bulgarian to reach outer space when he boarded Soyuz 33 along with Soviet cosmonaut Nikolai Rukavishnikov.

Russian attempts to interfere continued after the People's Republic of Bulgaria and the Soviet Union collapsed.

A later President, Georgi Parvanov of the Bulgarian Socialist Party, sought energy cooperation in a programme that he termed a 'Grand Slam'.

This was opposed by former Prime Minister and current Party of European Socialists leader Sergei Stanishev, who had promised to replace the right wing government of Boyko Borisov.

[citation needed] Bulgaria was deemed "unfriendly to Russia" on 30 of April 2021, because of the expulsion of several diplomats.

[32] Bulgaria is close to selling two unused Russian-made nuclear reactors and other critical equipment to Ukraine's state-owned atomic energy company.

[33] In July Bulgaria took over the Rosenets oil terminal at the port of Burgas, run by Lukoil, with the Russian company losing its long term concession.