With the clock ticking towards added time in a tense encounter, the shaggy-haired centre back rose above the defence and crashed a 73rd-minute header into the net to send the European champions into Sunday's showpiece with Netherlands.
It was the 32-year-old's third international goal in his 89th appearance and puts Spain in their first World Cup final.
"Puyol the shark has taken us to the final," his jubilant Barcelona team-mate David Villa, who is joint top scorer at the tournament in South Africa with five goals, told reporters.
Puyol's all-round performance was "spectacular", Villa said while midfielder Xabi Alonso added: "There were 10 minutes where we were camped outside their penalty area but didn't score and then Puyol arrived like a young wild boar and scored."
Spain's Prime Minister Jose Luis Rodriguez Zapatero, who is a Barcelona fan, added his voice to the acclaim, telling Spanish radio: "What a leap, what a header by Puyol! He is superb."
Germany coach Joachim Low criticised his team for not picking out Puyol's run into the area but acknowledged the "massive power" and "great determination" he demonstrated.
"This was a set piece and there's always a mistake if you concede a goal at a set piece," Low said at a news conference.
"There were two of our defenders somewhere close and we should have anticipated the ball," he added.
"We didn't do that ... and Puyol approached us too quickly and thumped the ball in."
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