International career

In June 2004, he debuted for Argentina, playing in an under-20 friendly match against Paraguay. In 2005 he was part of a team that won the 2005 FIFA World Youth Championship in the Netherlands. There, he won the Golden Ball and the Golden Shoe, scoring in the last four of Argentina's matches and netting a total of six for the tournament.
He made his full international debut on 17 August 2005 against Hungary at the age of 18. He was substituted on during the 63rd minute, but was sent off on the 65th minute because the referee, Markus Merk, found he had headbutted defender Vilmos Vanczák, who was tugging Messi's shirt. The decision was contentious and Maradona even claimed the decision was pre-meditated. Messi returned to the team on 3 September in Argentina's 1–0 World Cup qualifier away defeat to Paraguay. Ahead of the match he had said "This is a re-debut. The first one was a bit short." He then started his first game for Argentina against Peru; after the match Pekerman described Messi as "a jewel".
On 28 March 2009, in a World Cup Qualifier against Venezuela, Messi wore the number 10 jersey for the first time with Argentina. This match was the first official match for Diego Maradona as the Argentina manager. Argentina won the match 4–0 with Messi opening the scoring.
On 17 November 2010, Messi scored a last-minute goal against South American rivals Brazil after an individual effort to help his team to a 1–0 win in the friendly match, which was held in Doha. This was the first time that he had scored against Brazil at senior level.

2006 World Cup

The injury that kept Messi from playing for two months at the end of the 2005–06 season jeopardised his presence in the 2006 World Cup. Nevertheless, Messi was selected in the Argentina squad for the tournament on 15 May 2006. He also played in the final match before the World Cup against the Argentine U-20 team for 15 minutes and a friendly match against Angola from the 64th minute. He witnessed Argentina's opening match victory against Ivory Coast from the substitute's bench. In the next match against Serbia and Montenegro, Messi became the youngest player to represent Argentina at a World Cup when he came on as a substitute for Maxi Rodríguez in the 74th minute. He assisted Hernán Crespo's goal within minutes of entering the game and also scored the final goal in the 6–0 victory, making him the youngest scorer in the tournament and the sixth youngest goalscorer in the history of the World Cup. Messi started in Argentina's following 0–0 draw against the Netherlands. In the following game against Mexico, Messi came on as a substitute in the 84th minute, with the score tied at 1–1. He appeared to score a goal, but it was ruled offside with Argentina needing a late goal in extra time to proceed. Coach José Pekerman left Messi on the bench during the quarter-final match against Germany, which they lost 4–2 on a penalty shootout.

2007 Copa América

Messi at the 2007 Copa América

Messi played his first game in the 2007 Copa América on 29 June 2007, when Argentina defeated United States 4–1 in the first game. In this game, he showed his capabilities as a playmaker. He set up a goal for fellow striker Hernán Crespo and had numerous shots on target. Tevez came on as a substitute for Messi in the 79th minute and scored minutes later.
His second game was against Colombia, in which he won a penalty that Crespo converted to tie the game at 1–1. He also played a part in Argentina's second goal as he was fouled outside the box, which allowed Juan Roman Riquelme to score from a freekick, and increase Argentina's lead to 3–1. The final score of the game was 4–2 in Argentina's favor and guaranteed them a spot in the tournament's quarterfinals.
In the third game, against Paraguay the coach rested Messi having already qualified for the quarter-finals. He came off the bench in place of Esteban Cambiasso in the 64th minute, with the score at 0–0. In the 79th minute, he assisted a goal for Javier Mascherano. In the quarter-finals, as Argentina faced Peru, Messi scored the second goal of the game, from a Riquelme pass in a 4–0 win. During the semi-final match against Mexico, Messi scored a lob over Oswaldo Sánchez to see Argentina through to the final with a 3–0 win. Argentina went on to lose 3–0 to Brazil in the final.

2008 Summer Olympics

Messi in the semi-final against Brazil at the 2008 Olympics

Having barred Messi from playing for Argentina in the 2008 Olympics, Barcelona agreed to release him after he held talks with newly appointed coach Josep Guardiola. He joined the Argentina squad and scored the first goal in a 2–1 victory over Ivory Coast. He then scored the opening goal and assisted Ángel di María in the second to help his side to a 2–1 extra-time win against the Netherlands. He also featured in Argentina's match against rivals Brazil, in which Argentina took a 3–0 victory, thus advancing to the final. In the gold medal match, Messi again assisted Di María for the only goal in a 1–0 victory over Nigeria.

2010 World Cup

Messi played the entire game on Argentina's opening match 1–0 victory against Nigeria. He had several opportunities to score but was repeatedly denied by Vincent Enyeama. Messi started in Argentina's following 4–1 win against Korea Republic; he participated in all of the goals of his team and helped Gonzalo Higuaín score a hat-trick. On the third and last group stage match Messi captained during Argentina's 2–0 win over Greece, again being the centrepoint of Argentina's play and was voted man of the match.
At the Round of 16 he assisted Carlos Tévez for the first goal in a 3–1 win against Mexico. The referee awarded that goal even though it was a clear offside. The World Cup ended for Argentina with a 4–0 loss against Germany.