Original Canterbury winter jacket Portsmouth FC 2007/09

Portsmouth Football Club is a professional football club based in Portsmouth, Hampshire, England, which compete in EFL League One. They are also known as Pompey, a local nickname used by both HMNB Portsmouth and the city of Portsmouth; the Pompey nickname predates the club and has various unconfirmed origin sources and theories. The club was founded on 5 April 1898 by Sir John Brickwood and began playing home matches at Fratton Park the following year. They compete against Southampton in the South Coast derby, a rivalry based in part to geographic proximity and both cities' respective maritime histories. Portsmouth are one of only five English football clubs to have been champions of all four tiers of the professional English football pyramid.

Portsmouth spent their early history in the Southern and Western leagues, winning five division titles before being admitted into the English Football League in 1920 as founder members of the Third Division. They won the Third Division South title in 1922–23 and were promoted out of the Second Division at the end of the 1926–27 season. They competed in the 1929, 1934 and 1939 FA Cup finals, winning the competition for the first time in latter of these finals and thereby remaining as reigning champions throughout World War II. They won the First Division title in 1948–49 and 1949–50 under the stewardship of Bob Jackson. However, their 32 consecutive years in the top-flight ended in relegation in 1959 and was followed by another relegation two years later, though the goals of Ron Saunders helped the club to win promotion as Third Division champions in 1961–62.

Portsmouth were relegated to the to the fourth tier for the first time in 1978, their second relegation in three years, though promotion out of the Fourth Division was secured in 1979–80 and was followed by another Third Division title in 1982–83. Promotion back to the top-flight was achieved in 1986–87, though they stayed there for just one season and then remained in the second tier between 1988 and winning the division in 2002–03. They spent seven seasons in the Premier League and lifted the FA Cup again under manager Harry Redknapp in 2008. They lost the 2010 FA Cup final after being relegated, which signalled the start of a difficult period where the club entered financial administration twice and were relegated three times, dropping down to the fourth tier in 2013. Portsmouth were saved from High Court liquidation after being bought out by the fan-owned Pompey Supporters Trust (PST) in April 2013. PST sold the club on to Michael Eisner after the League Two title was won at the end of the 2016–17 campaign. Portsmouth went on to win the EFL Trophy in 2019.