That is the astonishing claim made by El Mundo, with the Spanish newspaper reporting on Sunday that it had obtained details of the deal signed by the 33-year-old in 2017.
The mega-money agreement, which expires in June this year, would see Messi receive up to €555,237,619 across four seasons, providing a number of conditions are met.
Messi was at the centre of a major transfer storm when he attempted to force a move away from Camp Nou last August, but was left frustrated when Barca refused to sanction an exit.
Amid a fraught presidential election campaign, it has remained apparent that all is not well at the Catalan club, whose financial worries are cast in a fresh light after El Mundo's stunning front-page revelations, with the outlet claiming to have laid hands on a copy of "the most sought-after document".
In addition to annual earnings in excess of €138m – dependent on some variables – the report says Messi received a renewal fee of over €115m, and a loyalty bonus just shy of €78m.
The Argentina international, who also rakes in millions in image rights, is said to have earned more than €500m from the eye-watering deal so far.
Barca's accounts for the 2019-2020 season showed gross debt had reached €820m, with the coronavirus pandemic having further dented their outlook.
Against the backdrop of those financial woes, Messi's desire to leave, and with a fractious presidential election not due to be concluded until March, Barca are still off the pace in LaLiga despite a run of four consecutive top-flight wins.
Messi, who was red carded for the first time in his career earlier this month, has contributed 15 goals in all competitions.