The third overall pick in the 2016 draft, Brown averaged a career-high 26.6 points, 6.9 rebounds and 3.5 assists a game last season helping Boston reach the Eastern Conference finals.
A twice NBA All-Star Brown will earn $28.5 million next season before his extension begins in 2024 averaging $60.8 million a year.
Brown's supermax deal tops two-time Most Valuable Player and reigning Finals MVP Nikola Jokic for the richest contract in NBA history.
The distinction of being the NBA's highest-paid player may not last long with Brown's Celtics teammate Jayson Tatum poised to assume the title next year when he becomes eligible for a supermax contract.