List of Portsmouth F.C. seasons

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 Association Football Club, that flourished from 1883 to 1896, the first goalkeeper of the professional era was Matt Reilly who previously played for the successful Royal Artillery team.

Portsmouth F.C. were formed on 5 April 1898 and coincidentally "replaced" the Royal Artillery Portsmouth club which had "retired" in 1899 after a professionalism scandal. Portsmouth were unusually elected straight into the first division of the Southern League, replacing Royal Artillery Portsmouth (who themselves had replaced the Southampton-based Freemantle F.C. in the 1897-98 season).

Portsmouth F.C.'s first ever 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 The league was won for the first time in the 1901–02 season, by which time Brettell had been replaced by club captain Bob Blyth as manager.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.

1910–11 saw Portsmouth relegated, but with the recruitment of Robert Brown as manager the team were promoted the next season.

The club has won the League Championship twice, the FA Cup twice, never won the League Cup, the Charity Shield once (shared).

This list details the club's achievements in all major competitions, and the top scorers for each season. Top scorers in bold were also the top scorers in the English league that season. Records of competitions such as the Hampshire Senior Cup are not included due to them being considered of less importance than the FA Cup and the League Cup.

Key

 * P = Played
 * W = Games won
 * D = Games drawn
 * L = Games lost
 * GF = Goals for
 * GA = Goals against
 * Pts = Points
 * Pos = Final position
 * Div 1 = Football League First Division
 * Div 2 = Football League Second Division
 * Div 3 = Football League Third Division
 * Div 3(S) = Football League Third Division South
 * Div 4 = Football League Fourth Division
 * Prem = Premier League
 * Champ = EFL Championship
 * Lg1 = EFL League One
 * Lg2 = EFL League Two
 * n/a = Not applicable
 * INT = Intermediate Round
 * GS = Group Stage
 * R1 = Round 1
 * R2 = Round 2
 * R3 = Round 3
 * R4 = Round 4
 * R5 = Round 5
 * QF = Quarter-Finals
 * SF = Semi-Finals
 * RU = Runners-up
 * W = Winners

Note: bold text indicates a competition won. Note 2: Where fields are left blank, the club did not participate in a competition that season.