Football is the most popular sport in Sofia, the capital of Bulgaria. Sofia was the first city in the country to have an organized football championship, which was created in 1921.The Danubian town of Vidin inaugurated its city championship the same year, while those of Ruse, Pleven and Rila (Southwestern Bulgaria) were created a year later. Most other regions followed suit in 1923. Teams from Sofia have been crowned national champions on 70 occasions in the 90 seasons between 1924 and 2013.Bulgaria – List of Champions, RSSSF.com. Retrieved Oct 2013. As of the late 20th and early 21st centuries, there are four teams from Sofia which have been constant participants in the top national division – Levski, CSKA, Slavia and Lokomotiv.Due to mergers, splits and general re-organization, all of these have had several different names over the years. See history and teams sections for details. All four have managed to reach the latter stages of European competitions on several occasions, the best of which are CSKA's two European Cup semi-finals in 1967 and 1982, and Slavia's Cup Winners' Cup semi-final in 1967.

History

Football has been played in Sofia as an organized sport since 1921, with some clubs having been founded more than a decade earlier. The Sofia Regional Sports Organization (SOSO) oversaw the running of the Sofia Sports League (SSL), until the creation of the national championship in 1948. The number of divisions in the Sofia league varied over the years and, in the early 1940s, reached a maximum of six divisions, with 43 teams competing in this "Organized" league system. Aside from them, there were dozens of so-called "Unorganized" teams playing outside this league in the Bulgarian capital, which at the time had a population of between 150 000 (1920) and half a million (1946) people.

The history of Sofia football follows the political life of Bulgaria, with all major upheavals having both direct and indirect effects on the shape and character of the clubs and their players. This history can be split into three broad periods, all of which are themselves subdivided into smaller sections. The three main periods are – the early 1900s–1944, during the Kingdom of Bulgaria; 1944–1989 during the communist People's Republic of Bulgaria; and 1989 to the present, during the so-called "Transition" (bg).

The early years, 1900s–1944

Organized sport did not develop in Bulgaria until the very end of the 19th century, as the country had only recently gained autonomy within the Ottoman Empire, in 1878. The earliest sports organizations began appearing as gymnastic societies, the most famous of which was the Yunak Gymnastic Society, founded in 1895.History of the Yunak Gymnastic Society. Retrieved Oct 2013. Football, if it featured at all, was merely one of many sports practiced at these societies. The very first specially oriented football clubs were formed towards the end of the first decade of the twentieth century, and did not begin officially registering themselves as such until several years later. Even then, most did not refer to themselves as football clubs, but rather as sports clubs, and the very first among them had the actual words "Football Club" or "Sports Club" as their official name – examples include Sofia's FK13, originally simply "Futbol Klub" (est. 1909, registered 1913), and Atletik, originally simply "Klub Futbol" (est. 1910, reg. 1913); later clubs were "Sportklub" (est. 1920), and "Sportist" ("Sportsman", est. 1923).

The first organized football match in the Sofia Sports League was played on 8 Sept 1921 between Sportklub and Pobeda, and ended with a 6–1 win for Sportklub.Football Almanac – Sofia 1921–1948, Nikola Hristov, Simelpress, Sofia, 2010. The SSL began in 1921 with ten teams, and gradually expanded until there were 23 teams playing in four divisions in 1926. Aside from a temporary split in the very first season, which led to the short-lived Sofia Sports Union (SSS) in 1922–23, the SSL was the sole organized league system in the city until it was disbanded in 1944.

In 1923, the Bulgarian National Sports Federation (BNSF) was created, which began organizing the national championship. As of the summer of 1924, this was held as a knock-out tournament at the end of each season, with the participation of all of the regional champions. The first edition was not completed, with SC Levski losing in the final to Vladislav Varna in 1925, and SC Slavia being the first Sofia team to win it, in 1928. Slavia were national champions on six occasions before 1945, Levski on three, and ZhSK and Vladislav Varna twice each.

In 1926, the first citywide knock-out tournament was created in Sofia, the Ulpia Serdica Cup, which existed until 1942. Levski won this cup four times and then boycotted it, after the club was not allowed to keep the trophy, as the rules stipulated.

A small series of changes occurred in club organization following the assassination attempt on the Tsar during the Sveta Nedelya bombing in 1925. A much wider-reaching wave of changes occurred ten years later, following the coup d'état by the Zveno organization in 1934, and the subsequent counter-coup by Tsar Boris a few months later, in 1935. Following this series of political upheavals, many small Sofia clubs were merged into larger ones, or else they underwent temporary or permanent name changes, depending on the political affiliations of their members.One of the largest such amalgamations was SC Tsar Boris III, formed in early 1935 in the northeastern suburb of Poduyane from Pliska (est. 1927 from three older clubs dating from 1919), Hadzhi Dimitar (est. 1924) and SS24 (est. 1920 as Tigar).

In 1937, the BNSF decided to replace the knock-out format of the national championship with a new National Division, which contained 10 teams. Four of these were from Sofia, which therefore left the SSL in order to participate nationally. The National Division existed for three seasons and, when it was disbanded, the Sofia teams from it returned to play in the capital, forming the "Sofia Regional Division". This was a sort of "Sofia Premiership", which sat above the Sofia 1st Division.Over the three seasons until 1940, two more Sofia teams had been promoted and none relegated, making a total of six. Upon returning to the SSL, they were joined in the Regional Division by Botev Sofia, who would have been promoted to the National Division not it not been disbanded.

After the creation of the national league in 1937, a new nationwide knockout competition was created. This cup tournament ran between 1938 and 1942, and on all 5 occasions was won by teams from Sofia, with FK13 winning it twice.The Tsar's Cup had been the trophy given to the National Champions ever since 1925. As of 1938, the Tsar's Cup became the trophy for the new knockout competition, while a new trophy was created for the national championship. For the benefit of this article, all references to "Tsar’s Cup" will refer solely to the knock-out competition after 1938.

Several amalgamations also occurred during the war, such as "Sportklub–Sredets", formed in 1942 from the amalgamation of Sportklub with two smaller clubs – the municipal workers' Sredets (est. 1936) and the Armenian émigrés' club Homentmen (est. 1918), which existed for two years until the Soviet Army entered Bulgaria in late 1944.

After the communist takeover in 1944, the number of teams in Sofia was drastically slashed through forced mergers, with the number of organized clubs dropping from 29 teams in 5 divisions in 1944 to 14 teams in 2 divisions in 1945. Over the following five years, the entire history of football in Sofia was effectively erased and started afresh with newly named and differently organized sports teams.

During the entire pre-communist period (1921–1944), the most successful club in Bulgaria was Slavia Sofia, with six national championships and 11 Sofia championships, followed by Levski, with five national and 8 Sofia championships. The next best teams in the Sofia championship were – Sportklub and ZhSK (once national and once Sofia champions each), AS23 (twice Sofia champions), FK13 (once), and Shipka (one national cup and one Ulpia Serdika cup winners). Other consistently strong teams, but which never won any major competitions, are Botev, Benkovski and Rakovski.Note that AS23, ZhSK and Botev won the Sofia Championship once each while it was effectively a "2nd Division" competition, as all of the strongest teams had at the time been playing in the national division.

The socialist period, 1944–1989

When the communist regime took over in September 1944, they implemented many changes in the Bulgarian sports scene. One of the immediate effects in Sofia was that many clubs immediately began to be renamed, merged, their boards of directors rearranged, and their assets transferred to the new entities (see below for details). One example is the team Knyaz Kiril,A pro-monarchy club, named in honour of the tsar's younger brother. which, in the days immediately following the beginning of communist rule, was initially renamed Fatherland Front, a month later this was changed to Poshtenski SK ("Post Office SC"), before being merged into Levski under the name PSK–Levski. Teams stopped being called "sports clubs", and rather began being referred to as "people's physical culture associations" – narodno fizkulturno druzhestvo, or NFD.

The DSO period – 1949–57

The most dramatic change occurred in 1949, when the country's entire sports structure was overhauled. On 19 Sept 1949, a decision was taken by the communist party that all sport in the country would be arranged into six national "Voluntary Sporting Organizations" (dobrovolna sportna organizatsiya, or DSO), set up along professional lines, following the model already extant in the Soviet Union. Thus, people would only be allowed to train within their respective industry-relevant DSO – so, for example, people working in light industry would have to go and train at the DSO Dinamo facilities, while people working in heavy industry would train at DSO Torpedo. Since the DSOs took over not only the assets but also the first-team players of the clubs they inherited, this meant that all of the players also received honorary jobs within the respective industry, and received their wages not through their DSO, but from the factory in which they were registered as workers, thus officially still remaining amateur players.This is also the reason why many Eastern Bloc countries could keep fielding all of their best sportsmen and women during Olympic Games throughout this period.