2005 Spanish European Constitution referendum

A referendum on the Treaty establishing a Constitution for Europe was held in Spain on Sunday, 20 February 2005. The question asked was "Do you approve of the Treaty establishing a Constitution for Europe?" (Spanish: ¿Aprueba usted el Tratado por el que se establece una Constitución para Europa?). The consultative referendum on ratification of the proposed Constitution for the European Union was approved by 81.8% of valid votes, although turnout was just 41.8%, the lowest since the end of the Franco era.

The referendum was not legally binding on the government, but paved the way for parliamentary ratification of the constitutional treaty, which happened in the Congress of Deputies on 28 April 2005, with a 319–19 result in favour of approval, and in the Spanish Senate on 18 May 2005 with a 225–6 result.