Earlier, twin forwards Marcus and Markieff Morris, last season's top scorers and rebounders, hired an agent and announced they would skip their senior seasons.
The 6-foot-3 Selby was rated the overall No. 1 prospect in the nation when Kansas coach Bill Self signed him last year, but was suspended the first nine games by the NCAA for amateurism violations. He also missed several more with a foot injury and wound up averaging 7.9 points, 2.2 rebounds and 2.2 assists in 26 games.
Selby had spent more than a week working out in Las Vegas testing NBA interest. He tweeted Thursday that he will miss Allen Fieldhouse, but was looking forward to "a new journey."
He added: "I will not return to Kansas next year. Making my dream a reality."
In a statement, Self said he supports Selby's decision.
"When the season was over, Josh, his family and I spoke quite candidly about what he wanted to do," Self said. "He made it very clear that he wanted to go to Las Vegas and work out to see if he could get more information of his NBA draft status. He did exactly what we agreed for him to do and handled it well and has come to the conclusion that it's best for him to go ahead and enter into the 2011 NBA draft. We, as a staff, totally support Josh's decision and we also hope our fans support it as well."
Selby's most memorable game as a Jayhawk was his first. With just seconds to go, he made a 3-pointer from the right wing to lift Kansas to a 70-68 victory over USC in Allen Fieldhouse on Dec. 18. His 21 points that day turned out to be his career high. He averaged 12 points and 3.2 assists his first 13 games but injured his foot on Feb. 1. He missed the next three games and was hampered the rest of the season.
"I never coached a kid that went through as much stuff his freshman year as Josh has," Self said. "He fought through it and certainly played through injury and did everything within his power to give our team the best chance to succeed.
"Josh made above a 3.0 [grade point average] his first semester and worked with his professors to complete his work second semester. I feel good about Josh leaving here knowing he took care of his business the way that he should have taken care of it."
The Jayhawks will need to be almost completely retooled next season. Seniors Tyrel Reed and Brady Morningstar are graduating and the Morris twins and Selby are leaving early for the NBA. Point guard Tyshawn Taylor and forward Thomas Robinson will be the only returning players who had significant roles in Kansas' seventh straight Big 12 regular-season championship.