Cristiano Ronaldo started his career in Portugal with Sporting Lisbon. He made his debut for the club in 2002, aged just 17.
A year later Manchester United decided they wanted him at Old Trafford. They spent £12m on Ronaldo, pictured here with Sir Alex Ferguson and Brazil footballer Kleberson.
Ronaldo played his first game for United at the start of the season in 2003. After coming on as a sub he helped United defeat Bolton Wanderers.
He started playing for Portugal in that season too, and starred at Euro 2004, helping his country knock out England on penalties in the quarter-finals.
By the 2005-06 season Ronaldo had improved a lot, but United weren't winning much as Chelsea were just too good. Ronaldo scored 12 goals in 47 games that season.
At the World Cup in 2006 Portugal knocked out England again. Wayne Rooney was sent off, and Ronaldo became very unpopular in England as a result.
Ronaldo was linked to a move to Real Madrid that summer, but stayed at Old Trafford and helped the club win the Premier League title in 2007.
It was a big season for Ronaldo on a personal level too, scoring 28 goals. He was named the Player's Player of the season and the Young Player of of the season.
Ronaldo hit top form in the 2007/08 season. He smashed in 32 goals in the league and scored 46 in all competitions. United won the Premier League and the Champions League.
Manchester United won the league for a third season in a row in 2009. They also reached the Champions League final, after beating Arsenal in the semi-finals.
When United picked up the Premier League trophy Ronaldo looked pretty happy to get his hands on it again.
But United didn't win retain their European Cup, losing 2-0 to Barcelona. The Champions League final proved to be Ronaldo's last game for United before his transfer.