Introduced at half-time, Messi finally broke the deadlock when his shot beat Levante goalkeeper Aitor Fernandez in the 62nd minute to start the celebrations at the Camp Nou.
Messi's league-leading 34th goal was his 46th in all competitions this season.
Barcelona's win puts the club nine points ahead of second-placed Atletico Madrid with three matches left to play.
Atletico beat Valladolid 1-0 earlier, forcing Barcelona to need a victory to wrap up the title this weekend before the club turns its attention to its upcoming European clash with Liverpool.
Barcelona won their second straight league title since Ernesto Valverde took over at the start of last season. It was also their eighth Liga crown in 11 years, a period during which Real Madrid has won two and Atletico one. Barcelona has 26 league titles, second only to Madrid's 33.
Barcelona are trying to complete a rare sweep of all three major titles this season. They host Liverpool on Wednesday in the opening match of their Champions League semi-final, and can win a fifth consecutive Copa del Rey if they beats Valencia in the final on May 25. Relive the action below.
Relive the action above.
Good evening and welcome to our live coverage of Barcelona vs Levante in La Liga.
And here are the lineups from the Camp Nou this evening
All Barcelona require tonight is a win to claim their eighth La Liga title in 11 years.
Their opponents this evening Levante sit just three points above the final relegation spot, but they did their confidence a world of good in midweek by hammering Real Betis 4-0.
However the side from Valencia, who have on loan Real Madrid strike Borja Mayoral among their ranks, will face a completely different proposition when they face the Catalan giants tonight.
The home side however will have to seal the title without Lionel Messi, from the start anyway, as Ernesto Valverde thinks ahead to their midweek Champions League clash with Liverpool.
This day was quite memorable for Barcelona fans last season, even if it may have been slightly tearful as well.
Victory tonight would of course wrap up the first of three trophies that Barcelona are chasing tonight, but it would be the first time since 2010 that they would win it in front of their home fans.
Four titles won away from home and won without playing have come since then, but it is not the only trophy the home support will hope to celebrate this season.
The Catalan giants have a huge Champions League semi-final clash against Liverpool, the first leg of which takes place on Wednesday at the Camp Nou.
And should they come through that and win the final in Madrid, they would have the opportunity to make it a treble by beating Valencia in the Copa del Rey final on May 25.
He may not be starting today, but the magician did conjure up this eight years ago.
The players are walking out to an expectant Camp Nou in the heart of Catalonia, with the La Liga holders' anthem blaring out.
Barcelona, who will be captained by Gerard Pique in the absence of Messi, face Levante for the fifth time inside 12 months.
This could be the start of a third treble in 12 years for Barca, so let's see if they can wrap it up tonight.
1 min: Barcelona 0-0 Levante
So we're underway here at the Camp Nou. A year to the day Iniesta played his last game for the club, will the hosts make more history on 27 April?
3 min: Barcelona 0-0 Levante
Early warning signs for the visitors, who are rescued by goalkeeper Aitor Fernandez, blocking a Luis Suarez effort at his near post after a fluid Barcelona move.
6 min: Barcelona 0-0 Levante
That's a huge chance for the hosts!
Having forced the corner with a long-range effort, Phillipe Coutinho picks out an unmarked Lenglet from a short corner, but the Frenchman doesn't get enough on it and his centre-back partner Pique cannot poke it in at the far post.
Living dangerously at the moment the visitors.
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