Hastings & St Leonards United was founded in June 1906, following a meeting between the directors of Hastings & St Leonards FC and St Leonards United. Both clubs had been struggling to meet the financial demands of professional football, and it was agreed that the town could not sustain two competing professional teams. A merger was therefore seen as the best way to protect the future of football in Hastings.
Founded around 1890 as Hastings Athletic, the club formed part of the Hastings Amateur Athletic Club, which also operated cricket, tennis, rugby, and athletics teams based at the Central Ground. The club adopted the name Hastings & St Leonards in 1895 and became a founding member of the East Sussex League the following year. They won the competition four times before leaving to join the South Eastern League for the 1904–05 season. This league included reserve sides from major professional clubs such as Arsenal, Tottenham Hotspur, Queens Park Rangers, and Brighton & Hove Albion, as well as first teams from Eastbourne, Tunbridge Wells, and Hitchin.
In 1905 the club turned professional, entering the Second Division of both the Southern League and the South Eastern League—following Hastings, who had taken the professional step a year earlier. At the same time, they changed their name to St Leonards United and moved into the newly laid-out Sports Ground, which they shared with Rock-a-Nore.
During the 1905–06 season it became increasingly clear that Hastings could not support two professional football clubs. Attendances were poor, both sides were operating at a loss, and discussions between the two boards concluded that a merger was the most viable solution. The united club adopted the name Hastings & St Leonards United.
The newly formed club played at the Sports Ground on the Brisco estate. Their colours were red and green—a blend of Hastings’ red and blue and St Leonards’ green and white. The first team took Hastings’ place in the South Eastern League Division One and St Leonards’ place in the Southern League Division Two. A reserve team filled St Leonards’ former spot in the South Eastern League Division Two.
Former Aston Villa and Grimsby player John “Jack” Griffiths was appointed trainer and served until 1909.
Over four seasons the club competed against sides such as Southend United, Wycombe Wanderers, and Brighton & Hove Albion Reserves in the Southern League, and against reserve teams from Arsenal, Tottenham Hotspur, and Chelsea in the South Eastern League. They also spent three seasons in the United League, facing strong teams including Norwich City, Watford, and New Brompton (later Gillingham FC).
One notable highlight was their FA Cup first-round match against Portsmouth in 1908.
The club’s main ambition was to win promotion to the Southern League Division One, and they came close in the 1909–10 season, only to lose 6–0 to Stoke in a play-off. Despite the quality of football, attendances fell short of expectations. To reduce costs, the playing squad was trimmed and the reserve team withdrawn ahead of the 1908–09 season.
By the summer of 1910, mounting financial losses forced the directors to wind up the club. Professional football did not return to the town until 1948, when Hastings United was formed.