| Competition: | Primeira Liga |
| Season: | 2005–06 |
| Dates: | 19 August 2005 – 7 May 2006 |
| Winners: | Porto 21st title |
| Relegated: | Gil Vicente Rio Ave Vitória de Guimarães Penafiel |
| Continentalcup1: | Champions League |
| Continentalcup1 Qualifiers: | Porto Sporting CP Benfica |
| Continentalcup2: | UEFA Cup |
| Continentalcup2 Qualifiers: | Braga Nacional Vitória de Setúbal |
| Best Player: | Ricardo Quaresma |
| League Topscorer: | Albert Meyong (17 goals) |
| Biggest Home Win: | Braga 5–0 Rio Ave (17 February 2006) |
| Biggest Away Win: | Maritimo 0–6 Vitória de Setúbal (20 November 2005) |
| Highest Scoring: | União de Leiria 5–2 Rio Ave (7 May 2006)[1] |
| Matches: | 306 |
| Total Goals: | 681 |
| Average Goals: | 2.23 |
| Prevseason: | 2004–05 |
| Nextseason: | 2006–07 |
The 2005–06 Primeira Liga was the 72nd edition of top flight of Portuguese football. It started on 19 August 2005 with a match between Sporting CP and Belenenses and ended on 7 May 2006. The league was contested by 18 clubs with Benfica as defending champions.
Porto and Sporting CP were both qualified for the 2005–06 UEFA Champions League group stage, and Benfica qualified for the UEFA Champions League qualifying round; Braga, Nacional and Vitória de Setúbal qualified for the 2006–07 UEFA Cup; in opposite, with the league dropping to 16 teams, four teams were relegated to the Liga de Honra; Gil Vicente, Rio Ave, Vitória de Guimarães and Penafiel. Meyong was the top scorer with 17 goals.
The season's first goal was scored by Rogério, who scored a 39th-minute goal for Sporting against Belenenses. The first yellow card of the season was given to Sporting's Fábio Rochemback in the opening game of the season, and the first red card was given to Benfica's João Pereira in his club's away draw against Académica de Coimbra.
Moreirense, Beira-Mar and Estoril were relegated to the Liga de Honra following their final classification in 2004–05 season.
The other three teams were replaced by Estrela da Amadora, Paços de Ferreira and Naval 1º de Maio from the Liga de Honra.
The Footballer of the Year award was won by the Portuguese Ricardo Quaresma of Porto, for a second successive season.
The Portuguese Golden Shoe award was won by the Cameroonian Albert Meyong of Belenenses, scoring 17 goals.
