Steph Houghton's third goal in as many games books Hope Powell's side a place in the last eight of the Olympic games, after Team GB Women top Group E with maximum points
Arsenal left-back Steph Houghton scored the only goal of the game and her third goal of the tournament after just two minutes to seal their passage to the last eight, while captain Kelly Smith also missed a second-half penalty.
Hope Powell was forced into making one solitary change for the Group E showdown, bringing in Sophie Bradley at the expense of Ifeoma Dieke after the 31-year-old suffered a ruptured cruciate ligament injury in the 3-0 win over Cameroon.
But Great Britain got themselves off to a dream start and took the lead after just two minutes through the woman of the moment, Houghton.
Team GB forced a corner on the far side, which was cleared only as far as Karen Carney and her low cross found the left-back in space before the Arsenal Ladies defender nipped around Brazil keeper Andreia Suntaque and angled her shot into the empty net to score her third goal in as many games and spark scenes of jubilation amongst the largely partisan crowd.
Brazil responded almost immediately, when Cristiane Rozeira de Souza Silva managed to wriggle free 25-yards from goal before sending a teasing drive just the wrong side of Karen Bardsley's post.
The WFC Rossiyanka striker should have levelled moments later too, when Carney was carelessly caught in possession midway inside her own half by Brazil skipper Marta Vieria de Silva, who threaded Cristaine through, but she couldn't find the target.
The 27-year-old was undoubtedly the visitors' biggest threat and she went close again midway through the first half when she turned to fire a shot straight at Bardsley following a sublime bit of skill from Thais Duarte Guedes on the right-hand side.
Jorge Barcellos' side were now in command and they were desperately unlucky not to level the score moments later when Alex Scott inadvertently headed a looping cross against her own upright with Bardsley stranded.
Team GB responded on the half-hour, however, through star striker Kelly Smith. She had been quiet by her own admission but sprung to life with a superbly executed volley, which flew past the far post after Jill Scott had nodded down Houghton's pin-point diagonal ball.
As Canarinhas made two changes at the break, introducing Daiane Menezes Rodriquez and Aline Pellegrino in place of Maurine Dorneles Goncalves and Bruna Beatriz Benites Soares as Barcellos switched from 3-4-3 to a 4-4-2 formation, but it was Team GB who started on the front foot after the interval and they should have been two goals to the good when Gunners striker Smith met Eniola Aluko's cross, but she could only head straight at Andreia.
At the other end, Bardsley had been relatively untroubled in the opening 45 minutes, but she had to be at full stretch to deny Renata Aparecida Da Costa's volley from creeping inside the near post.
Aluko's pace had been causing Brazil problems in the second period and she lashed wide from close range before Powell's side were given the chance to put the game to bed from the penalty spot just shy of the hour mark.
Aluko raced clear of the visitors' defence before being cynically tripped by Francielle Manoel Alberto, who was only booked, but Smith watched on in horror as Andreia turned away her weak effort.
And Team GB were almost immediately made to pay for their captain's wastefulness from the spot, when Marta skipped by Scott and drilled a powerful low effort at the feet of Bardsley.
The tireless Aluko was then replaced by Rachel Yankey, but it was Houghton who showed her defensive capabilties with a superb sliding challenge in the penalty box to thwart the onrushing Daiane.
Brazil came close to snatching a last-gasp equaliser, but Rosana Dos Santos Augusto's drive found the grateful clutches of Barsley as the South Americans had to settle for second place in Group E and the prospect of world champions Japan in the last eight.