Spain's governing conservative party has won the most seats in the general election but has lost its majority and must now try to form a coalition.
The liberal Ciudadanos party was in fourth place with 40 seats.
Podemos and Ciudadanos fielded national candidates for the first time, boosted by discontent among the electorate.
The PP and the Socialists have alternated running the government for more than three decades.
A spokesman for Podemos said the results showed that two-party politics in Spain had ended.
"We are entering a new era in our country," said Inigo Errejon.
Prime Minister Mariano Rajoy's PP needed 176 seats to form a majority. It had 186 seats in the outgoing parliament.
"I will try to form a government, a stable government," Mr Rajoy told PP supporters, after the final results were announced.
Read more: Spanish election: PM Rajoy's party loses majority - BBC News