Italy Serie B

The first Italian football championships were composed of a small number of teams. It was in 1904 that the tournament expanded with the first edition of the Seconda Categoria (Second Category): this was a competition in which, on one side, the reserve teams of clubs affiliated with the Prima Categoria (First Category) participated, and on the other side, those provincial clubs that had recently joined the Italian Football Federation (FIGC).

For the provincial teams, it wasn't enough to beat the reserve teams of the metropolitan clubs by winning the second-tier championship: they had to prove to a Federal Technical Commission that they had acquired a sufficient level of technical ability to compete with the first-team players of the Prima Categoria. Therefore, they were required to demonstrate this in a unique test match, not comparable to a play-off, a match against a Prima Categoria team in front of prominent football figures of the time. The first team to reach the honour, was Pro Vercelli in 1907, which even won the scudetto in 1908.

The status quo was challenged by a federal official with a letter published in the football columns of La Gazzetta dello Sport in February 1912: according to him, there was no movement between the Prima Categoria and the Seconda Categoria, which had to bear the expenses of an entire season only to see them wasted by a single match against the reserve teams of the larger clubs. The official proposed the introduction of a promotion-relegation system, which immediately gained the support of many clubs. As a result, several proposals for changes to the current Championship Regulations were drawn up in preparation for the annual Federal Assembly. This mechanism was introduced by the Federal Assembly on August 31, 1912, where the Valvassori-Faroppa plan was approved. This plan modified the Italian football pyramid, turning the Seconda Categoria into the new Promozione (Promotion) championship and creating a dedicated championship for Reserve teams. Just as the Seconda Categoria had been managed in the past, the Promozione was entrusted to the Regional Committees, which the FIGC had established in 1909.

It wasn’t until 1921 that the Pozzo Plan, made by manager Vittorio Pozzo, created a true national second-tier league by establishing the Seconda Divisione (Second Division), a tournament in which all the clubs affected by the heavy trimming of the Prima Categoria, now renamed Prima Divisione (First Division), participated. The new introduced regulations, strongly supported by the secessionist Italian Football Confederation (CCI) (which applied them starting in the 1921–22 season) and approved along with the Pozzo Plan, involved the division of Italy into two large geographical areas, managed by the North and South Leagues, with a sharp cut at the center of the country. This meant teams from Tuscany played in the North, and those from Marche and Umbria played in the South. As a result, the Seconda Divisione experienced two different sets of rules, due to the stark geographical and organizational differences: in the North, the league was organized outside the regional framework directly by the Lega Nord, while in the South, it was still managed by the Regional Committees because the distances and means of transportation didn’t allow for interregional league management. Only in the 1925–26 season did the Lega Sud of major clubs organized the regional Seconda Divisione groups directly. The first teams to be relegated (1921-22 season) were Vicenza and Inter Milan even if, after the CCI reunion with FIGC, the regulations were changed, and Venezia was demoted instead of the Milanese club.

In the north, the new competition started in the 1922–23 season with 48 teams divided into six groups, structured at the interregional level but still vaguely corresponding to the jurisdictions of the regional committees. By 1924–25, the number dropped to 40 teams and four groups, now geographically more extensive. In the south, not all Regional Committees managed to organize the Seconda Divisione championship immediately, which was especially difficult in the island regions, where the number of regulation-sized fields was minimal. The first season saw about 25 teams participating, and by the following season, this increased to 40, but problems related to the particularly troubled political era began to emerge. Few clubs managed to complete all four championships organized by the Lega Sud between 1922–23 and 1925–26 due to high operating costs.

In 1926, the Viareggio Charter renamed the top league to Divisione Nazionale (National Division), consequently renaming the lower categories, with the Seconda Divisione becoming the Prima Divisione. The two bodies managing the tournament, the Lega Nord and Lega Sud, were merged into a national governing body called the Direttorio Divisioni Superiori (Directory of Higher Divisions). This led to one of the groups being reserved for southern clubs, with many northern teams effectively relegated by default.

The far-reaching reform envisioned by the Viareggio Charter was completed in 1928 by the new FIGC president, the fascist politician from Bologna, Leandro Arpinati. The influential politician established the creation of a radically different second-tier league within a year, meaning no longer an interregional tournament but a single national group, exactly like the one planned for the top league. Thus, in 1929, the Serie B of the Divisione Nazionale was born. The establishment of a single group for the second-tier league sparked protests from smaller clubs, who complained about the high travel costs for matches across the entire country and the lower gate receipts compared to the top league. They unsuccessfully proposed expanding the first edition of Serie B of the Divisione Nazionale to two groups based on territorial criteria, admitting the semifinalists of the southern Prima Divisione championship by default. The two-group formula would have reduced the high operating costs of participating in the second-tier league and given more representation to the central and southern teams. However, the proposal was not accepted, and Serie B remained a single group.

The first edition saw 18 teams registered, a format that remained unchanged until the 1933–34 season, when an attempt was made to divide into two groups based on geography (west and east). However, this experiment was unsuccessful, and in 1935–36, the original model was reinstated, which, except for an attempt to reduce the number of teams between 1936 and 1938, continued until the break caused by World War II.

In the immediate post-war years, the colossal wartime destruction and widespread poverty made it impossible to immediately restart the competition. The tournament developed with different formats between the two areas of the country, north and south. In the 1946–47 and 1947–48 seasons, the Serie B was played with a three-group format (geographically divided into northwest, northeast, and central-south). In the 1948–49 season, the FIGC finally managed to recreate a single group with 22 teams, reduced again to 18 teams in the 1952–53 season. In the 1958–59 season, the league was expanded to 20 teams, a format that, except for one occasion (the 1967–68 season, with 21 teams due to the reduction from 18 to 16 Serie A teams), remained unchanged for 35 years.

It was the consequences of the so-called "Caso Catania" in the 2003–04 season that disrupted this consolidated tradition and brought the number of participating teams to a record high of 24, later reduced to 22 the following year.

From 1946, both Serie A and Serie B were ran by Lega Calcio. However, on 30 April 2009, after divisions between Serie A and Serie B clubs regarding the future of the league, 19 of 20 top-flight clubs (the only exception being Lecce) agreed on plans to split from Serie B to form another governing and financing body. Subsequently, on 1 July 2010, the Lega Calcio has officially ceased to exist and was replaced by the two newly formed leagues, Lega Serie A and Lega Serie B.

In the 2018–19 season, due to the bankruptcy of Avellino, Bari, and Cesena to register, and the inability to quickly relegate teams (by the deadline for presenting the 2018–19 season fixtures), the second-tier league once again had an odd number of teams, dropping from 22 to 19. By FIGC order, in the 2019–20 season, the league returned to having 20 teams, a format that had been in place from 1968 to 2003.

The second-tier league, following the example of the top division, introduced the VAR system: from 2018 to 2021, it was used only for the play-offs and play-outs, while starting from the 2021–22 season, it was implemented for the entire regular season.

Serie B is the lowest division in which five historic clubs have ever played: Torino, Juventus, Milan, Roma and Lazio.