— Houston Rockets (@HoustonRockets) July 8, 2017
Harden, 27, is coming off a career-best season, during which he put up averages of 29.1 points, an NBA-leading 11.2 assists and 8.1 rebounds per game.
The MVP runner-up has two years and $59 million left on his current deal.
The four-year extension carries a value of $170 million and is the richest extension in NBA history.
With the megadeal, Harden is taking advantage of brand-new CBA rules that enable contract extensions for superstars. He became eligible to add four years to his deal after making the All-NBA team in May, and the Rockets became focused on locking him into an extension after their season ended.
“Houston is home for me,” Harden said in a statement released by the Rockets. “[Owner Leslie Alexander] has shown he is fully committed to winning, and my teammates and I are going to keep putting in the work to get better and compete for the title.”