This is a list of seasons played by Portsmouth Football Club in English and European football, from 1899 (the year of the club's first FA Cup entry and elected straight into the first division of the Southern League) to the most recent completed season. Football was played in the city of Portsmouth from the 1850s and was popular for sailors and dockers to play in the city. The current club was founded in 1898 with John Brickwood, owner of the local brewery, as chairman, and Frank Brettell as the club's first manager.
A common myth is that the club's first goalkeeper was Sir Arthur Conan Doyle. While Conan Doyle did play as AC Smith for an amateur side, Portsmouth Athletic Football Club, that flourished from 1882 to 1894, the first goalkeeper of the professional era was Matt Reilly who previously played for the successful Royal Artillery team.
Portsmouth was formed to replace the defunct Royal Artillery Portsmouth club, and elected straight into the first division of the Southern League. The club's first league match was played at Chatham Town on 2 September 1899 (a 1-0 victory), followed three days later by the first match at Fratton Park against local rivals Southampton. That first season was hugely successful, with the club winning 20 out of 28 league matches, earning them runners-up spot in the Southern League. The league was won for the first time in the 1901-02 season, by which time Brettell had been replaced by club captain Bob Blyth as manager.
The 1906-07 season was highlighted by the visit of Manchester United to Fratton Park in the FA Cup, which generated a record attendance of 24,329. A 2-2 draw meant a replay in Manchester, and Portsmouth recorded a famous 2-1 win. However, this record attendance was surpassed two seasons later when Sheffield Wednesday visited Fratton for the second round of the new FA Cup.