ESPN's Adrian Wojnarowski reported the news.
The 32-year-old Italian had one of the best seasons of his career, averaging 18.7 points, 5.2 rebounds and 1.9 assists while shooting 40.5 percent from three-point range.
Although he'd already started the transition from small forward to becoming a stretch power forward during his final season with the Denver Nuggets and two years with the Clippers, the 6'10", 233-pounder played the position almost exclusively during his stay in Oklahoma City.
It's a change that seemed to benefit his overall game. Not only does it fit his skill set as a strong outside shooter, but he's always been a mediocre defender with a career minus-0.6 defensive box plus-minus, per Basketball Reference. Playing as a stretch 4 avoids matchups against the NBA's top wing players.
As long as Gallinari can stay healthy, he has the potential to be an impact player for the Hawks. Injuries have been a significant part of his career, and he hasn't played more than 70 games in a season since 2012-13.
Gallinari's scoring ability will fit in nicely with a Hawks team that ranked 17th in the NBA in points per game (111.8) and 26th in offensive rating (107.2) last season.
Even though Gallinari isn't going to do much to improve their last-ranked defense, his shooting touch will mesh nicely with Trae Young's ability as a playmaker.
Young often relied on himself to make things happen for Atlanta's offense in 2019-20 because the rest of the roster struggled in shooting situations. John Collins had a strong year with 21.6 points per game and a 40.1 three-point percentage, but no one else averaged more than 12.3 points.
The Hawks were the least-efficient three-point shooting team in the league last season, making just 33.3 percent of their attempts.
Gallinari will be an immediate improvement in that category and bring a strong veteran presence to an Atlanta team that is looking to take significant steps forward coming off a 20-47 record.