Boyko Metodiev Borisov (born 13 June 1959) is a Bulgarian politician who served as Prime Minister of Bulgaria on three separate occasions, serving a total of 9 years between 2009 and 2021, making him the country's longest-serving post-communist Prime Minister. A member of the GERB party, which he founded and currently leads, he previously served as Mayor of Sofia from 2005 to 2009. Borisov remains politically active to date and currently serves as a Member of the National Assembly.

Borisov was elected mayor of Sofia in 2005. In December 2005, he was the founding chair of the conservative political party Citizens for European Development of Bulgaria (GERB), becoming its lead candidate in the 2009 general election. Borisov led GERB to a landslide victory in 2009, defeating the incumbent Socialist Party, and resigned as mayor of Sofia to be sworn in as prime minister. He resigned in 2013, following nationwide protests against the government's energy policy, but after leading GERB to victory in the 2014 general election, he was again named Bulgaria's prime minister. His second term ended similarly to his first, after Borisov resigned in January 2017, this time following GERB's defeat in the 2016 presidential election. As before, Borisov led GERB to election victory again in the snap 2017 general election, becoming prime minister for a third time.

Borisov-led governing coalitions, Bulgaria experienced an improvement in macroeconomic situation and general political stability; however, it remained the EU's poorest member state (in terms of GDP per capita), with nearly a quarter of its population living below the national poverty lines. Foreign direct investment fell, and corruption has led, as recently as June 2019, to repeated rejection of Bulgaria's attempts to join the Schengen Area. Electoral results for Borisov and his party were overshadowed by allegations of fraud in 2013, 2015, and in 2019, both locally and for the European Parliament. Judicial threats and attacks against journalists increased to the point where journalism in Bulgaria became "dangerous" according to Reporters Without Borders, which ranked Bulgaria 111th globally in press freedom in 2019. In 2019, former U.S. Ambassador to Bulgaria James Pardew stated that a "national political environment with little government or criminal accountability and no serious opposition to challenge the current government" was in place as a result of collusion, corruption, and stifling of the media under Borisov. On 17 March 2022, Borisov was detained after allegations of misuse of EU funds; he was released after spending 24 hours in prison.

In 2013, Borisov became the oldest person ever to play for a Bulgarian professional club when he appeared for FC Vitosha Bistritsa in the B Group, the second division of Bulgarian football.

Borisov was born in 1959 in Bankya (then a village, today a town, part of Stolichna Municipality) to the Ministry of Internal Affairs official Metodi Borisov and elementary school teacher Veneta Borisova. Borisov has claimed that his grandfather was executed by the communists for being a Nikola Petkov supporter in the wake of the 1944 Bulgarian coup d'état. This has been disputed, however, as Nikola Petkov was still an ally of the communist insurgents in 1944. Furthermore, Borisov's later rise within the ranks of the communist-era security services would have been unlikely with such a family background. Other sources point out that Borisov's grandfather either died during a criminal incident or that both his grandfathers died peacefully in the 1960s and 1970s.

In 1977, Borisov graduated from Bankya High School with excellent grades. Between 1982 and 1990, he assumed different positions in the Ministry of Internal Affairs as a firefighter and later as a professor at the Police Academy in Sofia. As a National Security Office member, Borisov took part in the protection of crops and haylofts during the name-changing campaign towards ethnic Turks in the 1980s. From 1985 to 1990, Borisov was a lecturer at the Higher Institute for Police Officers Training and Scientific Research of the Ministry of Interior.

Borisov quit the Ministry in 1991 with the rank of major, after formally refusing to renounce his Communist Party membership or "depoliticise". In 1991, he founded a private security company, Ipon-1. He subsequently became bodyguard to Bulgaria's last communist leader, Todor Zhivkov, after the latter was overthrown in 1989, and to Simeon II. Borisov has been claiming participation in karate championships since 1978, serving as the coach of the Bulgarian national team and a referee of international matches. He said to United States President Barack Obama that he has a 7th dan black belt in karate, but his coach denied this, and stated that Borisov has never even been a karate competitor, but only an administrator of the team.

Borisov is divorced, but for a number of years lived with Tsvetelina Borislavova, head of Bulgarian American Credit Bank. Borisov has a daughter, Veneta, from his former marriage to the physician Stela. Borisov also has a sister, Krasimira Ivanova.