Parliamentary elections were held in Bulgaria on 25 June 2005, for the 240 members of the National Assembly. According to exit polls, the Socialists had a lead with around 31%, but without a majority, necessitating the creation of a coalition. The National Movement for Simeon II, in power before the election, was in second place, with around 21%. Following the election, Socialist Party leader Sergei Stanishev became Prime Minister.

The Bulgarian Socialist Party, also known as The Centenarian, is a centre-left, social democratic political party in Bulgaria. The BSP is a member of the Socialist International, Party of European Socialists, and Progressive Alliance. Although founded in 1990 in its modern form, it traces its political heritage back to the founding of the BRSDP in 1891. It is also Bulgaria's largest party by membership numbers.