The Giants completed a four-game sweep of the Tigers with a 4-3 victory in 10 innings.
Marco Scutaro, the most valuable player in the National League Championship Series, was again the hero for the Giants, cracking a sharply hit single into shallow centre to bring in Ryan Theriot with the winning run.
Having survived six do-or-die elimination games in the National League Division and Championship Series, the Giants closed out the season in ruthless style, reeling off seven consecutive wins.
"What made them so special was they were such an unselfish group, they just loved each other and played for each other and for the fans and had a never say die attitude," Giants manager Bruce Bochy said.
"It's amazing what a group of guys who play like a team can accomplish."
Brandon Belt opened the scoring with an RBI triple in the second and Buster Posey added a two-run homer in the sixth while reliever Santiago Casilla took credit for the win.
After back-to-back shut-outs and 20 scoreless innings, Detroit's batters finally awoke from their slumber with Triple Crown winner Miguel Cabrera and Delmon Young both hitting home runs, but it was too little too late.
No team has ever erased a 3-0 deficit to win a World Series and the Tigers dug the hole a little deeper when they fell behind 1-0 in the second inning.
Hunter Pence doubled to the wall in deep centre for Giants’ first hit then trotted home when Belt drilled a triple into the right field corner to silence the sell-out crowd.
But Tigers fans were back on their feet cheering wildly in third when Cabrera took a 1-1 offering from Giants ace Matt Cain and crushed a towering two-run homer into the right field bleachers to give Detroit their first lead of the series.
Posey answered with a two-run blast in sixth that slipped just inside the left field foul pole, but the fireworks continued in the bottom of the inning with Young launching a solo shot over the right field wall to tie the game at 3-3.
Tigers had a glorious opportunity to take control in the eighth when Avisail Garcia was issued a lead-off walk with their big bats lined up to drive in the go-ahead run.
But Giants reliever Jeremy Affeldt defused the threat striking out Cabrera, Fielder and Young.