Results breakdown of the 1977 Spanish general election (Congress)

This is the results breakdown of the Congress of Deputies election held in Spain on 15 June 1977. The following tables show detailed results in each of the country's 17 autonomous communities and in the autonomous cities of Ceuta and Melilla, as well as a summary of constituency and regional results.

Electoral system
348 members of the Congress of Deputies were elected using the D'Hondt method and a closed list proportional representation, with an electoral threshold of three percent of valid votes—which included blank ballots—being applied in each constituency. Seats were allocated to constituencies, corresponding to the provinces of Spain, with each being allocated an initial minimum of two seats and the remaining 248 being distributed in proportion to their populations, at a rate of approximately one seat per each 144,500 inhabitants or fraction greater than 70,000. Ceuta and Melilla were allocated the two remaining seats, which were elected using plurality voting. The use of the electoral method resulted in an effective threshold based on the district magnitude and the distribution of votes among candidacies.

As a result of the aforementioned allocation, each Congress multi-member constituency was entitled the following seats:

Voting was on the basis of universal suffrage, which comprised all nationals over 21 years of age and in full enjoyment of their civil and political rights.

The electoral law allowed for parties and federations registered in the interior ministry, coalitions and groupings of electors to present lists of candidates. Parties and federations intending to form a coalition ahead of an election were required to inform the relevant Electoral Commission within fifteen days of the election call, whereas groupings of electors needed to secure the signature of at least one-thousandth of the electorate in the constituencies for which they sought election—with a compulsory minimum of 500 signatures—disallowing electors from signing for more than one list of candidates.