It was the name of the top-level football league in the Republic of Ireland from its foundation in 1921 until the introduction of a second division in 1985.

The inaugural season featured eight teams from County Dublin, all of whom had spent the 1920–21 season playing in the Leinster Senior League: Bohemians, Dublin United, Frankfort, Jacobs, Olympia, St James's Gate, Shelbourne and YMCA.

Among the new members were Shamrock Rovers, who would win the title at the first attempt, and Athlone Town, who became the first team from outside County Dublin to compete in the League.

The League continued to expand both numerically and geographically during its first two decades, with Dundalk being elected in 1926–27 and subsequently becoming the first team from outside County Dublin to win the title in 1932–33.

Dundalk were subsequently joined by Waterford in 1930–31, Cork Bohemians in 1932–33, Sligo Rovers in 1934–35 and Limerick in 1937–38.

[3] The 1950s was marked by the emergence of St Patrick's Athletic and the re-emergence of Shamrock Rovers, with the former winning the title at the first attempt in 1951–52 and claiming two more in the middle of the decade, and the latter winning their first title in fifteen years in 1953–54.

The FAI aims to recruit 20 clubs in total for the new league, split into north and south divisions.

Apart from the current twenty members, at least 38 other clubs have competed in the League of Ireland at one time or another.

League of Ireland games are broadcast by both RTÉ and Virgin Media Television.

[18][19][20][21] In 2015 the FAI agreed a deal with TrackChamp to stream all Premier Division and First Division games outside Ireland, but the deal was criticised by customers as the streaming service required registration for a betting platform.

[22] In 2024 attendances across the League of Ireland broke the million mark for the first time ever; a total of 1,001,630 fans went to games in the SSE Airtricity Men's Premier Division, First Division, SSE Airtricity Women’s Premier Division, men's and women's FAI Cups, the All-Island Cup and European matches.