Del Piero (left) and Grosso scored to put Italy into the final
An absorbing semi-final seemed set for penalties until Grosso curled man of the match Andrea Pirlo's pass past Jens Lehmann with just one minute left.
Del Piero then finished an Italy break with a delicate chip into the corner.
Germany's Lukas Podolski earlier sent a header wide and saw a shot saved, but the hosts' Cup dreams were shattered.
There were, unsurprisingly, tears among German players and fans after the extraordinary end to an enthralling encounter - in which Italy also hit the woodwork twice in extra-time.
The opening 90 minutes were intriguing - but goalless - and it was in the extra period that the game truly exploded into life.
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The Italians, famed for their defensive strength, adopted an increasingly attacking approach, aware of the Germans' brilliant record at penalty shoot-outs.
Substitute Alberto Gilardino's shot rebounded off the post and Gianluca Zambrotta's drive struck the bar.
But Podolski led the German attacking threat, missing the header from David Odonkor's cross and forcing a brilliant one-handed save from Gianluigi Buffon.
Del Piero then squandered a shooting chance from the edge of the box after great work from Vincenzo Iaquinta and Francesco Totti and Pirlo forced a diving save from Lehmann.
Jurgen Klinsmann was left in despair by Italy's late goals
But Pirlo still had time to have his say as, with Italy pushing forward in numbers, he threaded the ball to Grosso whose first-time shot left Lehmann with no chance.
The goal was timed at 119 minutes and Germany, and their supporters who had crammed into Dortmund's Signal Iduna Park, were stunned.
And as Jurgen Klinsmann's side pushed forward in desperation, Gilardino found the ball in space and rolled it to Del Piero who sent a clinical finish beyond the advancing Lehmann into the roof of the net.
The opening 90 minutes saw Italy work the first clear opening as Totti's astute pass picked out Simone Perrotta, but Lehmann smothered the ball.
Fabio Cannavaro, exceptional throughout the match, marshalled the Italian back line effectively and limited Germany in the opening period.
Italy saw a Pirlo free-kick on 24 minutes elude both Luca Toni and Marco Materazzi by a fraction.
606 VIEW Italy deserved it, Cannavaro was at his very best
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Then Toni was played in by Grosso, only for his goalbound shot to be blocked by Per Mertesacker.
Germany, however, fashioned the best chance of the first half, but Bernd Schnieder shot over after finding rare space behind the Italian defence.
Buffon had to make his first real save, and had to race from his goal to block as Miroslav Klose danced his way into the area.
Germany were on top and Buffon parried a close-range effort from Podolski 12 minutes later.
But extra-time seemed inevitable as Michael Ballack, not at his imperious best, sent a free-kick over the top from 20 yards.
Indeed, the 90 minutes ended without a goal - opening the dramatic extra period in which Grosso and Del Piero wrote themselves into Italian football history.
Their delight at the final whistle was in stark contrast to Germany, who were left bereft as their dream of lifting the World Cup on home soil came to a sudden, heart-breaking end.
Germany: Lehmann, Friedrich, Metzelder, Mertesacker, Lahm, Borowski (Schweinsteiger 72), Ballack, Kehl, Schneider (Odonkor 83), Klose (Neuville 111), Podolski.
Subs Not Used: Jansen, Huth, Nowotny, Hanke, Kahn, Asamoah, Hitzlsperger, Hildebrand.
Booked: Borowski, Metzelder.
Italy: Buffon, Zambrotta, Cannavaro, Materazzi, Grosso, Camoranesi (Iaquinta 90), Perrotta (Del Piero 104), Gattuso, Pirlo, Totti, Toni (Gilardino 74).
Subs Not Used: Zaccardo, Barzagli, Peruzzi, Nesta, Amelia, Barone, Inzaghi, Oddo.
Booked: Camoranesi.
Goals: Grosso 119, Del Piero 120.
Att: 65,000
Ref: Benito Archundia Tellez (Mexico).
Fifa man of the match: Andrea Pirlo
TRIVIA
By defeating hosts Germany, Italy have reached their sixth World Cup final, denying Germany a record eighth final appearance. The Italians are now in position to become the second nation to have won at least four World Cup trophies.
Italy have now kept five clean sheets and have conceded only one goal (an own goal by Cristian Zaccardo) in the tournament. Their five shut-outs equals a record for a nation in a World Cup campaign.
Germany joined Chile (1962), Italy (1990) and South Korea (2002) as hosts to have been halted in the semi-finals. Their defeat was the third in a World Cup match that was decided in extra time. They also fell to England in the 1966 final (4-2) and to Italy in the 1970 semi-finals (4-3).
Trivia stats source: Infostrada Sports
50px Two stylish Italian goals minutes from the end of the second period of Extra Time prevented a penalty kick shootout and sent Germany out of the FIFA World Cup in Dortmund on Tuesday.

Signal Iduna Park

Despite the best attacking efforts from the two teams, the score had remained level during 90 minutes of regulation time and the 28 overtime minutes that preceded the game winner.

Moments after Jens Lehmann had dived to put Andrea Pirlo's 25 yard drive behind for a corner, the German keeper was helpless. With the clock on 119 minutes Fabio Grosso, found in the area by Pirlo, circled a left foot shot across him just inside the far post.

Just two minutes later, Alessandro Del Piero got Italy's second with the last kick of the game when he clipped high past Lehmann's left hand at the end of a fast break-away with Alberto Gilardino.

Lehmann had the busier match and made eight saves while Gianluigi Buffon was troubled by two. The Arsenal goalkeeper had also to deal with twelve corner kicks, many of which he plucked easily from the Italian heads.

Germany played the game without ball winner Torsten Frings, whom FIFA had suspended from the match for a punch thrown in a melee after the penalty shootout in the quarter-final against Argentina. 

In the 90 minutes the better chances fell to Germany. On half an hour Bernd Schneider was free on goal but did not keep his shot down. After an hour Lukas Podolski, right of goal, spun and shot but was denied by Gianluigi Buffon.

The Italian defence had not conceded a goal for four games, and were to go on to record a fifth shut out in six games at the World Cup finals. 

The statistics suggest Italy were the most attacking side in the match with eight more corners, nine more offsides and 14 per cent more ball possession than their opponents.

Italy played overtime with a vigorous intent to win and nearly cracked the Germans in the first two minutes. Gilardino cut back from the goal line and got away a sneaky near post shot but it bounced off the inside of Lehmann's left post. Gianluca Zambrotta drove one from the edge of the area but was denied by Lehmann's crossbar.

The Germans who had gone the full 120 minutes in their last game appeared the more tired team but had a chance to go 1-0 in front. Lukas Podolski was found unmarked at the near post, but his header from ten yards was about ten yards wide.

Italy had an emotional history of penalty kick shootout losses at the World Cup, including a defeat in the 1994 World Cup final, but Marcello Lippi's team's persistence was eventually rewarded. There were no penalties to overcome.  Germany has won a total of five World Cup penalty shootouts in a row.

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