Harlequins (officially Harlequin Football Club) is a professional rugby union club that plays in Premiership Rugby, the top level of English rugby union. Their home ground is the Twickenham Stoop, located in Twickenham, south-west London.

The club, which was founded in 1866 as "Hampstead Football Club", split the following year with some of the membership forming Wasps RFC. Three years later Hampstead renamed itself Harlequins and became one of the founding members of the Rugby Football Union in 1871. For more than a hundred years, Harlequins had been one of the top UK teams during the amateur era and this continued with the introduction of professionalism in 1995. The club has been champions of England twice, winning the title in 2012 and most recently in 2021. They won the European Challenge Cup in 2001, 2004 and 2011, and the domestic cup in 1988, 1991 and 2013.