Olynyk, who celebrated his 22nd birthday with the announcement, averaged 17.8 points (a team high), 7.3 rebounds and 1.1 blocks a game while being selected to the all-America first team this past season.
Gonzaga went 32-3 on the season, including 16-0 in the West Coast Conference. The Bulldogs held the No. 1 ranking in the USA Today Coaches' poll when the NCAA Tournament started.
"I love this place, I love my teammates but the NBA has been a dream of mine since I was a little kid, so it was something I had to act on," Olynyk said. "It's your dream. That's the highest level and everyone wants to play at the highest level. It will be a journey but I think it will be a fun one."
Olynyk graduated in December with a 3.53 grade point average and was named men's basketball Scholar Athlete of the Year by an Athletic Directors Association.
"We are very proud of what Kelly was able to accomplish at Gonzaga, both on the court and in the classroom," said Bulldogs Coach Mark Few. "The fact he was the Academic all-American for all of college basketball is a great example of what he is all about. We wish him all the best in his next challenge."