1991 Portuguese legislative election

The 1991 Portuguese legislative election took place on 6 October. The election renewed all 230 members of the Assembly of the Republic. There was a reduction of 20 seats compared with previous elections, due to the 1989 Constitutional revision.

The Social Democratic Party, under the lead of Cavaco Silva, won a historic third term and won an absolute majority for the second consecutive election. While it lost 13 MPs due to the reduction of the overall number from the original 250 to 230, although just a 3 seat loss if the 1987 election results are tabulated with the new seat distribution, it gained a higher share of the vote than in 1987. Cavaco Silva became the first Prime Minister since Hintze Ribeiro, in 1904, to lead a party into three successive democratic election victories.

The Socialist Party, at the time led by Jorge Sampaio, the future President of Portugal, increased its share by 7% and gained 12 MPs, a gain of 16 if compared with 1987 with the new seat distribution, but did not manage to avoid the absolute majority of the Social Democrats. Like four and six years earlier, and like 1979 and 1980, the PS failed to win a single district. In the first legislative election after the fall of the Eastern Bloc, the communist dominated Democratic Unity Coalition lost much of its electoral influence, losing almost 10 MPs and 4% of the voting, but were able to hold on to the district of Beja by a slight margin over the PSD.

On the right, the CDS could not recover its past influence, mainly to the effect of tactical voting for the Social Democratic Party by right-wing voters, increasing its parliamentary group by only 1 MP. The National Solidarity Party, using a populist campaign, achieved for the first time an MP, in what would be the only presence of such party in the Parliament.

Voter turnout fell to 67.8%, and for the first time below 70% of the electorate.