The 2008–09 Primeira Liga was the 75th season of the Primeira Liga, the top professional league for Portuguese association football clubs. It began on 22 August 2008 and ended on 24 May 2009. Porto was the three-time defending champions and secured a fourth consecutive title for the second time in its history.
Boavista were also relegated as a punishment for their participation in a match fixing scandal in 2003–04 season. Accordingly, Paços de Ferreira, which was originally scheduled to be relegated, was saved from demotion.
Leiria and Boavista were replaced by two promoted teams from Liga de Honra. The first was Trofense, which clinched the second level title. This was its first appearance in Primeira Liga.
Trofense was accompanied by Rio Ave, which returned to the Primeira Liga after two seasons in the Liga de Honra.
^ abPaços de Ferreira ahead of Estrela da Amadora on head-to-head record; Paços de Ferreira–Estrela da Amadora 1–0, Estrela da Amadora–Paços de Ferreira 0–2.