The 1999–2000 Primeira Liga was the 66th season of top-tier football in Portugal.
The league was contested by 18 clubs with Porto as the defending champions.
Benfica, Boavista, qualified for the UEFA Cup; in opposite, Vitória de Setúbal, Rio Ave and Santa Clara were relegated to the Segunda Liga.
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.