The Argentine, who has spent his entire club career at the Nou Camp since making his debut in 2004, was expected to sign a new deal after his previous contract expired in July.
But the Blaugrana have now officially confirmed that their all-time leading scorer will depart on a free transfer.
A statement read: “Despite FC Barcelona and Lionel Messi having reached an agreement and the clear intention of both parties to sign a new contract today, this cannot happen because of financial and structural obstacles (Spanish Liga regulations).
“As a result of this situation, Messi shall not be staying on at FC Barcelona. Both parties deeply regret that the wishes of the player and the club will ultimately not be fulfilled.
“FC Barcelona wholeheartedly expresses its gratitude to the player for his contribution to the aggrandisement of the club and wishes him all the very best for the future in his personal and professional life.”
Messi was free to negotiate a transfer with other clubs after his deal ran out at the end of June, but Barcelona had always maintained he wanted to stay with the club. The 34-year-old was reported to sign a new five-year deal.
Messi had tried to leave Barcelona in August 2020, making a formal request for an exit after a break down in his relationship with then president Josep Maria Bartomeu but successor Joan Laporta, who presided over the Argentine's rise to greatness, convinced him to stay.
Messi, who joined Barca's youth set up aged 13, is the club's all-time top scorer and appearance maker with 672 goals in 778 games in all competitions.
Factfile on Lionel Messi
Full name: Lionel Andres Messi Cuccitini
Date of birth: June 24, 1987 (34 years old)
Place of birth: Rosario (Argentina)
Nationality: Argentinian (also holds Spanish citizenship)
Height: 1m 69 (5 foot 7)
Weight: 72 kilos (158 lb)
Club: FC Barcelona (Since 2004)
151 caps and 76 goals for Argentina
Copa America (2021)
Under-20 World Cup (2005)
Four Champions Leagues (2006, 2009, 2011, 2015)
Ten La Liga titles (2005, 2006, 2009, 2010, 2011, 2013, 2015, 2016, 2018, 2019)
Seven Spanish Cups (2009, 2012, 2015, 2016, 2017, 2018, 2021)
Three European Super Cups (2009, 2011, 2015)
Eight Spanish Super Cups (2005, 2006, 2009, 2010, 2011, 2013, 2016, 2018)
Three Club World Cups (2009, 2011, 2015)
Six Ballons d'Or (2009, 2010, 2011, 2012, 2015, 2019)
Six Golden Boots (2010, 2012, 2013, 2017, 2018, 2019)
Twice elected UEFA player of the year (2011, 2015)
Best player at 2014 World Cup
Best player at the Copa America (2015, 2021)
Six times top scorer in the Champions League (2008-2009: 9 goals; 2009-2010: 8 goals; 2010-2011: 12 goals; 2011-2012: 14 goals; 2014-2015: 10 goals; 2018-2019: 12 goals)
Eight times Spanish League top scorer (2009-2010: 34 goals, 2011-2012: 50 goals, 2012-2013: 46 goals, 2016-2017: 37 goals, 2017-2018: 34 goals, 2018-2019: 36 goals, 2019-2020: 25 goals, 2020-2021: 30 goals)
Best player at the 2008 Olympics
Best player at the 2005 Under-20 World Cup
Record Ballons d'Or wins (6 to date)
Top goalscorer in Spanish League history (474 to date)
Most goals scored for one Spanish League club (474 for Barcelona)
Top overall goalscorer in Barcelona's history (672)
Top scorer in history for one club (672 for Barcelona)
Top scorer in Spanish 'clasicos' between Barcelona and Real Madrid (26)
Most appearances for Barcelona (778)
Most goals scored in a top class league season (50 in 2011-2012)
Top scorer in Argentina's history 76 (2006 to date)
Record goals scored in a calendar year (91 in 2012)
Record goals scored for a club in a season in all competitions (73 in 2011-2012).
Ronald Koeman has extended his hand to Lionel Messi by calling him “the best” as Barcelona get ready to play their first game since Argentine’s failed attempt to leave this summer.
The Argentina star has already been ruled out of the team's trip to Florida for a one-off friendly against Napoli in Miami on Wednesday.
Messi's 789th goal in his 1,000th career appearance — but first in the knockout rounds of the World Cup -- helped set up a last-eight clash with the unbeaten Netherlands on Friday.
The qualifying round matches will start at 10am on Sunday, while the main round matches will start from Monday. The final will be played on Saturday evening (December 11).
The Netherlands, bidding to win their first World Cup after losing in three previous finals, will face Argentina or Australia in the last eight.