| Competition: | Primeira Liga |
| Season: | 1999–2000 |
| Dates: | 20 August 1999 – 14 May 2000 |
| Winners: | Sporting CP 17th title |
| Relegated: | Vitória de Setúbal Rio Ave Santa Clara |
| Continentalcup1: | UEFA Champions League |
| Continentalcup1 Qualifiers: | Porto (third qualifying round) |
| Continentalcup2: | UEFA Cup |
| Continentalcup2 Qualifiers: | Benfica (first round) Boavista (qualifying round) |
| Matches: | 306 |
| Total Goals: | 739 |
| League Topscorer: | Mário Jardel (37 goals) |
| Biggest Home Win: | Porto 5–0 Farense (20 December 1999) |
| Highest Scoring: | Benfica 6–2 Farense (20 February 2000) |
| Longest Wins: | 4 games[1] Boavista Sporting CP |
| Longest Unbeaten: | 12 games Sporting CP |
| Longest Winless: | 8 games Rio Ave Vitória de Guimarães |
| Longest Losses: | 5 games Campomaiorense |
| Prevseason: | 1998–99 (Primeira Divisão) |
| Nextseason: | 2000–01 |
The 1999–2000 Primeira Liga was the 66th season of top-tier football in Portugal. The competition was renamed Campeonato Nacional da Primeira Liga (National Championship of the First League), Primeira Liga for short, after the Portuguese League for Professional Football took control of the two top nationwide leagues in 1999. It started on 20 August 1999 and ended on 14 May 2000. The league was contested by 18 clubs with Porto as the defending champions.
Sporting won their first Championship in 18 years (since 1981–82) and qualified for the 2000–01 UEFA Champions League first group stage, along with Porto, who qualified for the thirdqualifying round. Benfica, Boavista, qualified for the UEFA Cup; in opposite, Vitória de Setúbal, Rio Ave and Santa Clara were relegated to the Segunda Liga. Mário Jardel was the top scorer with 37 goals.
Beira-Mar, Chaves and Académica, were consigned to the Liga de Honra following their final classification in 1998–99 season.
The other three teams were replaced by Gil Vicente, Belenenses and Santa Clara from the Liga de Honra.
| Team | Outgoing manager | Manner of departure | Date of vacancy | Position in table | Incoming manager | Date of appointment | |
|---|---|---|---|---|---|---|---|
| Sporting CP | Mirko Jozić | Resigned | 7 June 1999[4] | Pre-season |  Giuseppe Materazzi | 16 June 1999[5] | |
| Sporting CP | Giuseppe Materazzi | Sacked | 27 September 1999[6] [7] | 4th | Augusto Inácio | 4 October 1999 | |
| Salgueiros | Dito | 7 November 1999 | 13th | Vítor Manuel | 10 November 1999[8] | ||
| Farense | João Alves | 5 December 1999 | 16th | Nicolau Vaqueiro | 12 December 1999 | ||
| Farense | Nicolau Vaqueiro | 8 January 2000 | 16th | Jorge Portela | 16 January 2000 | ||
| Vitória de Setúbal | Carlos Cardoso | 8 January 2000 | 17th | Rui Águas | 16 January 2000 | ||
| Farense | Jorge Portela | 29 January 2000 | 15th |  Ismael Díaz | 6 February 2000 | ||
| Vitória de Guimarães | Quinito | 24 April 2000 | 6th | António Valença | 30 April 2000 |
| Rank | Player | Club | Goals[9] |
|---|---|---|---|
| 1 |  Mário Jardel | Porto | 37 |
| 2 |  Alberto Acosta | Sporting CP | 22 |
| 3 | Gaúcho | Estrela da Amadora | 21 |
| 4 | Nuno Gomes | Benfica | 18 |
| 5 | Brandão | Vitória de Guimarães | 16 |
| 6 | Mariano Toedtli | Marítimo | 13 |
| 7 | Hugo Henrique | Rio Ave | 12 |
| 8 |  Lucian Marinescu | Farense | 11 |
| Whelliton | Boavista | 11 | |
| 10 | Edmilson | Vitória de Guimarães | 10 |
| Maniche | Benfica | 10 | |
| Odair | Braga | 10 |
