Jiracek scored with a stylish second-half strike to earn the Czech Republic a 1-0 win over Poland, putting the Czechs through to the quarterfinals and knocking out the co-host of Euro 2012.
With the victory, the Czechs finished top of Group A, and will play the runner-up of Group B in the knockout stage in Warsaw next week.
After withstanding a first-half barrage from Poland, the Czechs pushed forward in the second half, looking for an opening. It came on the counter in the 72nd minute, when Jiracek collected a pass from Milan Baros in the box, cut right to clear past Poland's Marcin Wasilewski and slotted the ball inside the far post.
"We had a poor start but we gradually improved, started to create chances and finally, we deserved to score," Jiracek said.
Poland coach Franciszek Smuda immediately brought on two attacking players in the last 30 minutes to push for an equalizer, but couldn't punch through the Czech defence.
After the final whistle, the Czech players swarmed around each other on the pitch, jumping and singing in front of the red-clad Czech fans who filled one corner of the stadium. The Poles fell to the ground, covering their faces.
"I think that probably we were too sure about winning this game. The Czechs played excellent football," Smuda said. "We had some opportunities before halftime, we didn't take advantage of them and we lost the game."
Smuda said his contract as head of the national team runs through Euro 2012, and he doesn't expect it to be renewed.
"My adventure with the national team is ending," he said.
The Czechs pulled off the win despite playing without their captain and playmaker Tomas Rosicky, who was sidelined with an Achilles tendon injury.
Without his creative skills the Czechs were listless in the first half, struggling to put together any fluid passing and reduced to knocking long balls forward.
The Poles, meanwhile, controlled the rhythm of play and created a host of chances before the break.
Their best opportunity came in the 10th minute when captain Jakub Blaszczykowski pounced on an errant pass deep in the Czech half and fed the ball to Robert Lewandowski in the area, only for the striker to slice his left-foot shot wide of the post.
But as the Poles pushed forward in the second half in search of a goal to put them through to the quarterfinals, more space began to open up in midfield.
That gave the Czechs the opportunity to strike on the counter, and the punishment came with Jiracek's second goal of the tournament. He also scored in the Czechs' 2-1 over Greece on Tuesday.
Poland responded well, though, and the final chances were all for the home team.
A cross from the right was deflected to the far post, where Marcin Wasilewski met the ball with a header that just cleared the bar. Minutes later, Blaszczykowski's angled effort was cleared off the line by Michal Kadlec as the Czechs sealed their place in the last eight.
"In the first half we had some chances and didn't take advantage of them," Blaszczykowski said. "With the time passing, we had to open up more and more, and I think this is the reason we conceded a goal on the counter."
The loss is a huge disappointment for Poland fans, who were hoping for the country's first ever victory at a European Championship — and a place in the quarterfinals.
The country had rallied around the team since the tournament opened on June 8, and their hopes had been boosted by the Poles' solid performances in their first two Euro 2012 matches — drawing 1-1 with Greece and Russia.
But even with the raucous support of the capacity crowd of 41,000 at Wroclaw's Municipal Stadium, the team failed to come through, against a Czech side playing without its best player.
The Czechs, meanwhile, showed unexpected grit and resolve after being crushed 4-1 by Russia in their tournament opener. They recovered to beat Greece 2-1, and then did just enough to get past Poland.
"I'm very happy that after the first match, when we didn't do very well, we were under pressure but won our remaining matches and we showed everybody that we're worth it," Jiracek said.
Czech Republic: Petr Cech, Theodor Gebre Selassie, Tomas Sivok, Michal Kadlec, David Limbersky, Tomas Hubschman, Jaroslav Plasil, Petr Jiracek (Frantisek Rajtoral, 84), Daniel Kolar, Vaclav Pilar (Jan Rezek, 88), Milan Baros (Tomas Pekhart, 90).
Poland: Przemyslaw Tyton, Sebastian Boenisch, Marcin Wasilewski, Damien Perquis, Lukasz Piszczek, Dariusz Dudka, Eugen Polanski (Kamil Grosicki, 56), Ludovic Obraniak (Pawel Brozek, 72), Rafal Murawski (Adrian Mierzejewski, 73), Jakub Blaszczykowski, Robert Lewandowski.