The XXI Constitutional Government of Portugal (Portuguese: XXI Governo Constitucional de Portugal) was the 21st government of the Third Portuguese Republic, under the current Constitution.

It was in office from 26 November 2015 to 26 October 2019, and was formed by the members of the Socialist Party (PS).

António Costa, leader of the PS, served as Prime Minister.

After the 2015 legislative election had resulted in a hung parliament, the leader of the Portugal Ahead alliance (PPD/PSD.CDS–PP), then Prime Minister Pedro Passos Coelho was given the task of forming a new government.

[1] In the meantime, Socialist Party secretary-general António Costa had succeeded in securing support for a Socialist minority government by the Left Bloc (BE), the Portuguese Communist Party (PCP) and the Ecologist Party "The Greens" (PEV), in a confidence and supply agreement.