Brazil stunned World Cup holders Spain in their Olympic women's football semi-final on Tuesday, winning 4-2 to set up a showdown with the United States in the gold medal match.

An Irene Paredes own goal gave Brazil an early lead in Marseille and Gabi Portilho doubled their advantage in first-half stoppage time.

Adriana made it 3-0 in the second half before a frantic finish saw Spain pull goals back via a Duda Sampaio own goal and a Salma Paralluelo effort, while Kerolin got Brazil's fourth.

Brazil are now guaranteed to at worst match their previous best showing in the Olympic women's football, when they won the silver medal in 2004 and 2008.

On both occasions they lost to the United States, who they meet again in Saturday's final at the Parc des Princes in Paris.

Meanwhile Spain, who are making their debut at the Games a year on from winning the World Cup for the first time, face Germany on Friday in Lyon in a play-off for bronze.

Brazil had scraped through their group as a best third-placed team, despite losing their last pool match to Spain, a game in which their legendary captain Marta was sent off.

She missed the quarter-final win over hosts France as a result and was again suspended here, but Brazil ultimately did not need her in either game.

The sixth-minute opening goal was farcical, with Spain goalkeeper Cata Coll blasting a clearance off Paredes and looking on as the ball ricocheted into the net.

Portilho, who scored the only goal against France in the last round, converted a cross from the left to make it 2-0 to Brazil right at the end of the first half.

Adriana came off the bench to seemingly put the game to bed on 71 minutes, scoring moments after her first attempt struck the crossbar.

Duda Sampaio deflected a Paralluelo header into her own net as Spain reduced the deficit late on, but Kerolin slotted a fourth for Brazil through the legs of Coll to end any doubt about the outcome as the match headed into a lengthy spell of injury time.

Paralluelo made it 4-2, but it was a night to forget for Ballon d'Or winner Aitana Bonmati and her teammates, even if they could still leave the Olympics with a medal.