In association football, a League Cup or Secondary Cup generally signifies a cup competition for which entry is restricted only to teams in a particular league. The first national association football tournament to be called "League Cup" was held in Scotland in 1946–47 and was entitled the Scottish League Cup. However, in the Republic of Ireland the now-defunct League of Ireland Shield was the first national league-only tournament of its kind (played first in 1921); this was subsequently replaced by the League of Ireland Cup in 1983.
The creation of a League Cup marked the difference from the Association Cup or Primary Cup, which is generally also open to teams from multiple leagues, often as far down as regional amateur leagues, and who are also members of the country's football association.
The creation of a tournament of this kind exclusively for the top national-level league teams, in addition to the two main domestic association football tournaments of the league and association cup, also created a new national footballing achievement called the domestic "treble". The first national league treble of this kind was won by Shamrock Rovers of the Republic of Ireland in 1925.
League cups were generally introduced after the Second World War – for example, the Football League Cup in England in 1960 – although in other countries they were created following a rise in the number of floodlit stadiums, allowing regular midweek matches.
In certain countries, the League Cup had, or in some cases still has, group stages in the early stages. These often opened the season before the main league season began.