Treaty United FC

The name of the club stems from Limerick's nickname as "The Treaty County", itself a reference to the Treaty of Limerick of 1691, the document which brought an end to the Williamite War in Ireland.

Following the liquidation of Limerick F.C. in 2019, the idea of a new team in Limerick arose. At first, it was to be called Limerick United but was forced to be changed due to threat of legal action from Limerick FC, because they had previously had that name. The name Treaty United was chosen as Limerick is known as the Treaty County, after the 1691 Treaty of Limerick. Treaty United was confirmed as the name, and the women's team Treaty United W.F.C. was ready to enter the 2020 Women's National League season and the men's the 2020 League of Ireland First Division, but the men's team withdrew their licensing application for the 2020 season. The club went through the licensing procedures the following year however and on 20 February 2021 it was announced by the Football Association of Ireland that the club had been granted a licence and would take part in the 2021 League of Ireland First Division, taking the place of Shamrock Rovers II from the previous season. Thus, the club is a continuation of senior football in Limerick, a story which began in 1937. In 2024, The club announced that it would switch primary kit colours from red and white stripes, which was an ode to the colours of the first senior football team in the county to blue and white, a colour that has been associated with football in the county since August 1943. The very presence of Treaty in the Markets Field is significant, as this is widely viewed as the historical, spiritual home of Limerick football.

The club announced their 26-man first team squad and backroom staff for their first season in football under manager Tommy Barrett on 27 February 2021. They also announced that the number 4 shirt would be retired as a mark of respect to former Limerick United captain Joe O'Mahony. The club's first senior men's fixture was a 1–1 draw with Waterford in a pre-season friendly on 2 March 2021, with Limerick local Joel Coustrain getting the honour of scoring the senior men's team's first goal. The senior men's first ever competitive fixture was on the 28 March 2021 as Treaty, captained by Jack Lynch, traveled to the Carlisle Grounds and drew 0–0 with Bray Wanderers to earn their first ever League of Ireland First Division point despite finishing the match with 10 men. The club finished in fourth place in their first season in the League of Ireland First Division.