Group A of the 2006 FIFA World Cup was one of eight groups in the opening round of the tournament. The group featured four teams, competition hosts Germany, Costa Rica, Poland and Ecuador. Play began on 9 June with the first game of the tournament between Germany and Costa Rica, with the former attaining a 4–2 victory in the highest scoring opening game in World Cup history since the competition introduced a single game opener. Later the same day, Poland and Ecuador faced each other, with Ecuador winning 2–0. On 14 June, Germany secured their second victory of the competition, defeating Poland 1–0 following Oliver Neuville's injury time goal. The following day, Ecuador defeated Costa Rica 3–0 to guarantee both they and Germany would advance to the round of 16.

The final set of matches was played on 20 June 2006. Germany and Ecuador contested the top place in the group, with the hosts winning 3–0. With both sides already eliminated, Poland defeated Costa Rica 2–1 to claim their only victory of the competition. Ecuador were eliminated in the following round by England while Germany reached the semi-finals before being defeated by eventual winners Italy. Germany finished third after beating Portugal in the third place playoff match.

Group A was the first of eight groups to start play at the 2006 FIFA World Cup in Germany. The competition consisted of 32 competitors, split into eight groups of four teams. The sides would play each other on a round-robin basis with the top two teams in each group advancing to the round of 16.

As hosts, three-time World Cup winners Germany qualified automatically for the tournament and were placed into Group A. Manager Jürgen Klinsmann had been appointed in 2004, but due to qualifying as hosts, had yet to take charge of his side in a competitive fixture. His team were considered one of the favourites to win the competition with bookmakers offering odds of around 13/2, but had received criticism in the country, notably from Bayern Munich general manager Uli Hoeneß who had labelled the side "a disaster". CONCACAF members Costa Rica endured a poor start to qualifying, narrowly avoiding an upset defeat against Cuba in the second qualifying round, before appointing Alexandre Guimarães as manager midway through the stage. They qualified for the tournament after finishing third in their qualification round, reaching the finals for the third time in their history. However, they were classed as rank outsiders to win the competition, with odds as high as 500/1 being offered.

To provide an even number of teams for the playoff bracket, the two teams from the UEFA qualification groups who had finished second in their group with the best record automatically gained qualification to the World Cup. Poland, who finished second in UEFA qualification Group 6 behind England, were one of the teams who were eligible, along with Sweden. Ecuador qualified after finishing in the third of four automatic qualification places in the CONMEBOL qualifying group behind Brazil and Argentina, reaching the finals for only the second time. Similar to Costa Rica, Ecuador were given low odds of around 400/1. In their preview of the tournament, The Guardian labelled Group A as the "weakest" in the competition.

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The opening match of Group A, and the World Cup, was between hosts Germany and Costa Rica. This was the first time the two sides had ever played each other in international football. Germany captain Michael Ballack was forced to withdraw from the starting line-up after failing to overcome an injury and was replaced by Tim Borowski. Defender Philipp Lahm gave Germany the lead after six minutes with a 30-yard curling shot from outside the penalty area that beat opposition goalkeeper José Porras and was described as "unstoppable" by the BBC. In doing so, Lahm became the fourth German player to have opened the scoring at a World Cup. Germany had further long range efforts soon after, before Costa Rica's Paulo Wanchope, already his country's record goalscorer, equalised after 12 minutes after breaching the German defence and finishing past goalkeeper Jens Lehmann. Wanchope's goal saw him become the first Costa Rican player to have scored in more than one World Cup and the second to have scored more than one World Cup goal after Rónald Gómez four years earlier.

Germany regained their lead five minutes later when Miroslav Klose finished from Bernd Schneider's cross. Costa Rica's Danny Fonseca became the first player to be booked in the competition after 30 minutes and the midfielder missed a chance to equalise shortly after half-time, heading wide despite being unmarked. Klose netted his second goal just after the hour-mark, putting in the rebound after his own header was parried by Porras. However, after 12 minutes Costa Rica again cut the deficit with Wanchope again scoring past Lehmann with a composed finish after receiving a cross from Walter Centeno, although the German players believed Wanchope was offside. The Germans sealed victory three minutes from time with Torsten Frings firing in a long-range shot that beat Porras in similar fashion to Lahm's goal. The six goals scored during the match made it the highest-scoring opening game in World Cup history since the tournament began using the single opening match format.