Veteran playmaker Xavi was the previous record-holder, having reached the milestone at the age of 25 years and 236 days. However, Messi has gotten there at just 24 years and 240 days old.
The Argentina international made his official La Liga debut in the 1-0 win over Espanyol on October 16, 2004 and has since developed into the Catalans' undisputed star player.
Indeed, going into the game against Valencia, Messi, who has won the Ballon d'Or for the past three years, had netted 142 times in 199 La Liga games for Barca.
The diminutive forward, who has played in every league game this season, is one of only five players in the current Barcelona squad to have made 200 or more league appearances for the club, with the others being the aforementioned Xavi (401), defender Carles Puyol (359), Victor Valdes (317) and Andres Iniesta (258).
Since November, Goal.com has been publishing exclusive extracts from Graham Hunter's highly-anticipated new book, 'Barca: The Making of the Greatest Team in the World'. The very last extract, which was published on Friday, looks at Andres Iniesta's risky return from injury in the 2009 Champions League Final and how he was described by Wayne Rooney as the 'best midfielder in the world'. Don't miss it!