Spain faces political uncertainty after two new movements won nearly a third of the seats in the country's election.
Anti-austerity party Podemos and liberal Ciudadanos made big gains as the conservative Popular Party lost its majority.
"Spain is not going to be the same anymore and we are very happy," said Podemos leader Pablo Iglesias.
The PP and the Socialists had alternated running the government for more than three decades.
The parties must now embark on negotiations to form a coalition.
The PP had 28.7% of the vote, the Socialists 22%, Podemos 20.6% and Ciudadanos 13.9%.