The loss ensured their trophy drought, which dates back to EURO 1996, will last at least another two years until the 2014 FIFA World Cup Brazil™ should Germany qualify.
Italian forward Mario Balotelli broke German hearts on Thursday with a first-half header and sublime strike as the inexperienced Germans - the youngest of the 16 teams at EURO 2012 - failed to cope with Cesare Prandelli's side.
Germany had a faint lifeline when Mesut Ozil converted a 92nd-minute penalty after a handball by Federico Balzaretti, but it was too little, too late as the perplexed looks in the German ranks told their own tale at the final whistle.
For all their potential and the impressive attack-minded football they showed in their EURO 2012 wins over Portugal, Holland, Denmark and Greece, Low's team did not have an alternative approach when things went wrong.
"The most bitter thing is that this team has so much potential for so much more," said Lahm as the Germans's 15-match winning streak in competitive games came to a halt. "But we weren't clever enough. If you don't show that potential at the right point in time, then you lose a game like that. It is a very, very bitter defeat.
"We made some stupid mistakes and we shouldn't have conceded the goals like that. If you find yourselves behind against the Italians, it is very hard to come back."
Having dropped three of his forwards for last Friday's 4-2 quarter-final win over Greece, Low again tinkered with his starting line-up, but this time it backfired as the Italians ruled the midfield in the first half.
Arsenal-bound Lukas Podolski was hauled off at half-time, striker Mario Gomez also made way for 34-year-old veteran Miroslav Klose after the break, while Toni Kroos barely troubled the Italian defence from the right wing. "I wanted to strengthen things in midfield, which is why I brought in Toni [Kroos]," explained Low.
"The goals we conceded came from mistakes, because we weren't present enough around the area. The cross from which Balotelli scored his opening goal shouldn't have been allowed to happen. We had things under control at the start, but after falling behind we took more risks and weren't as well organised.
"After going 2-0 down, we had to risk everything. The team showed a lot of heart in the second half, but when you find yourself 2-0 down against the Italians it is incredibly difficult."
Having finished third at the last two FIFA World Cups and lost the EURO 2008 final, this is the fourth consecutive tournament the Germans have reached at least the semi-final.