All three are products of the club's famed 'La Masia' academy.
Messi has scored an astronomical 90 goals in 2012 and is widely considered to be one of the greatest players of all time at the age of only 25.
He has set a number of club scoring records - including 25 goals in 16 La Liga games this season - and is favourite to win a fourth World Player of the Year award next month. He has been the top scorer in the Champions League for four years in a row.
Xavi, 32, is held in similar regard as the creative hub of the midfield and holds the record for most appearances with the club with 651. Puyol is second with 568.
Puyol, who made his debut in 1999 and took over the captaincy of the Blaugrana in 2004 - the year Messi made his debut - will be 37 when his new deal expires.
A club statement read: "FC Barcelona announces that it has reached an agreement with Carles Puyol, Xavi Hernandez and Leo Messi to renew their contracts.
"Carles Puyol, who had a contract ending June 30, 2013, is expanding his relationship with the club until June 30, 2016.
"Xavi Hernandez, who had a contract ending June 30, 2014 depending on appearances, has a contract that will finish on June 30, 2016.
"Leo Messi, who had a contract ending June 30, 2016, is expanding his relationship with the club until June 30, 2018.
"Thus Barcelona strengthens its ties with three key players.
"In the coming weeks and individually, Carles Puyol, Xavi Hernandez and Leo Messi will sign their new contracts."
Xavi's new deal is not contingent upon appearances.
Barca have raced to a nine-point lead over Atletico Madrid at the top of La Liga and stand 13 points clear of hated rivals Real Madrid, who are third, after Tito Vilanova took over following the departure of Pep Guardiola at the end of last season.
Messi scored two goals in a 4-1 win at home to Atleti at the weekend after Falcao opening the scoring for the Rojiblancos.
Puyol and Messi have won three Champions Leagues, five Liga titles and two Copa del Reys - all with Puyol as captain - while Xavi also won the Liga title in 1999 as he made his debut the year before the defender.
Puyol and Xavi also won the 2008 European Championship and 2010 World Cup with Spain, while Xavi won the 2012 Euros which Puyol sat out through injury.