Walcott grew up in the small village of Compton near Newbury. His first 11 a side game came when he was staying round schoolfriend Adam Walkers' house and was asked if he could play for his team Steventon boy's as they were a player short. He then played for his local side AFC Newbury. His most memorable game there was in 2000, when Newbury's Under-11 side beat Down Grange Albion 4-2 in the Peter Houseman League Cup Final. Walcott also scored over 100 goals (including mini tournament) in his one and only season for Newbury, before leaving there for Swindon Town. He then left Swindon Town for Southampton.

In the 2004-05 season, he starred in the Southampton youth side that reached the final of the FA Youth Cup against Ipswich Town. In addition, he became the youngest person to play in the Southampton reserve team, aged just 15 years and 175 days, when he came off the bench against Watford in September 2004. However, he did not play in the Premier League, as Southampton were relegated at the end of the 2004-05 season to the Championship. Despite having not yet played in the first team, at the age of 14, Nike agreed a sponsorship deal with Walcott.

Before the start of the 2005-06 season, Walcott linked up with the first team's tour of Scotland, just two weeks after leaving school. The striker then went on to become the youngest-ever player to play for the Southampton first team when he made his first team debut aged just 16 years and 143 days, after coming on as a substitute in Southampton's 0-0 draw at home to Wolverhampton Wanderers in the Football League Championship.

Walcott made his full first team debut away to Leeds United on 18 October 2005, scoring his first senior goal in the same game. He continued his scoring spree four days later away at Millwall before scoring again on his full home debut against Stoke City the following Saturday. His rapid rise to fame also led him to be named amongst the top three finalists for the prestigious BBC Sports Personality of the Year Young Personality award on 11 December 2005.

Before breaking into the Southampton first team Theo's massive potential was showcased in the 2006 MATCH Annual. The awesome attacking prospect was named by Britain's best-selling football magazine as, 'The Next Big Thing'!

His performances soon attracted attention from the British media, who saw him as one of the most promising young English talents of his time. There was speculation that Walcott would move to the Premiership and media reports linked him with some of the league's top clubs including Arsenal, Chelsea, Liverpool, Manchester United and Tottenham Hotspur as well interest from the likes of Real Madrid, Juventus, Milan and Barcelona. After much tabloid speculation, and intense and protracted interest from Chelsea in particular, Walcott ultimately signed for Arsenal on 20 January 2006 for an initial fee of £5m, rising to a possible £12m based on appearances for club and country, making him the most expensive 16-year-old in the history of British football.

On 7 February 2006, Walcott made his debut for Arsenal reserves in a game against Portsmouth reserves at Havant; he scored, but Arsenal lost 3-2. Walcott was then named in an 18-man squad to face Real Madrid in a UEFA Champions League second round first-leg tie at the Bernabéu on 21 February 2006.

On 28 February 2006 Walcott was included in the England Under-19 squad alongside Arsenal team mate Kerrea Gilbert to face Slovakia in a friendly at Sixfields Stadium. England won 3-0 on the night with Walcott scoring on his U19 international debut, with an 80th minute penalty kick. His original kick was saved, but the referee ordered the penalty to be retaken and Walcott scored on his second attempt.

On 16 March 2006, Walcott's 17th birthday, he finally signed a professional contract worth a reported £1 million a year, which lasts until summer 2008 and includes provisions to extend it.

On 19 August 2006, Walcott made his Premier League debut on the first day of 2006-07 season. He came on as a substitute after 73 minutes against Aston Villa. He played a significant role in creating Gilberto Silva's equaliser in the 84th minute. Upon receiving the ball in the penalty area, he sent in a floating cross towards the far post. The ball skimmed Robin van Persie's head before falling onto the path of Gilberto Silva, who made no mistake and scored the equaliser.

Walcott made his Champions League debut in the second leg of Arsenal's third qualifying round match against Dinamo Zagreb and became the youngest ever Arsenal player to appear in European competition, a record previously held by Cesc Fàbregas. Within minutes of coming on he received his first yellow card in Arsenal colours for taking a shot several seconds after the referee had already blown for offside. During stoppage time, however, his cross beat the Dinamo defence and Mathieu Flamini scored, giving Walcott an enviable record of two assists in two substitute appearances.

Walcott made his first Arsenal start on 14 October 2006 in the home game against Watford, impressing many on his much-anticipated full debut.

Walcott has since made his second full start for Arsenal in the 2-0 Carling Cup win over West Brom, in which he is credited for one assist.

He was of great influence in the UEFA Champions League match between Arsenal and Hamburg on the 21st of November, when he once again came off the bench and provided the ball to Emmanuel Eboue to make the scoreline 2-1 to Arsenal, and did the same several minutes later to Julio Cesar Baptista to help Arsenal win 3-1

--Wikipedia