"We are honored and thrilled to have been chosen to become the new stewards of the Hawks," Ressler said in a statement. He is the co-founder of Ares Management, an investment firm.
Former NBA All-Star Grant Hill and Spanx founder Sara Blakely are among the minority shareholders in Ressler's ownership group.
The sale, if approved, will mark the end of a saga that began with the publication last September of a 2012 email from Levenson, in which he said the team's ticket sales were lagging because its black fan base was keeping whites away from games.
The comments came to light as the NBA was embroiled in a scandal over recordings of then-Los Angeles Clippers owner Donald Sterling making racist comments to a female friend. Levenson had emerged as a major Sterling critic.
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The Hawks' general manager, Danny Ferry, has also been on indefinite leave since last September after making racially insensitive remarks during a conference call.
After Levenson's email became public, he quickly handed control of the team over to its chief executive officer, Steve Koonin.
The NBA in January approved plans to sell the franchise and it was announced the team would remain in Atlanta.
Atlanta Mayor Kasim Reed's office declined to comment on word of the deal.
Ressler, co-founder of Ares Management LP, an investment firm, was a finalist to purchase the Clippers last spring.
The Hawks are in the first round of the NBA playoffs after finishing first in the Eastern Conference.
Goldman Sachs & Co and Inner Circle Sports advised Atlanta Hawks on the deal.