Sánchez has been prime minister since June 2018. His Socialist party finished second in the last election, in 2023.
Although the conservative People’s Party won the most seats, it fell short of a majority.
Sánchez remained in power after striking agreements with left-wing parties and securing support from Catalan and Basque nationalist and pro-independence groups.
Most opinion polls suggest the conservatives are likely to emerge as the largest party in the next election. However, they would be expected to need the support of the hard-right Vox party to form a government.
Speaking after Monday’s announcement, the leader of the People’s Party, Alberto Núñez Feijóo, said: “At last, Spaniards will be able to decide”.
The opposition leader said it would not be “just another election”, but a chance for voters to choose between “decline or change, lies or change, incompetence or change, division or change, corruption or change”.
