"I'm making it official," Simmons said Sunday night.
The 6-foot-10 Australian led the Tigers in scoring (19.2 points), rebounds (11.8) and assists (4.8) this season.
"We knew that there was a great possibility that Ben would only be at LSU for one season," LSU coach Johnny Jones said Monday. "And if you are going to have a guy to do that, Ben was the perfect one because of how much of a team player he is."
LSU finished 19-14 and 11-7 in the SEC and failed to make the NCAA tournament. The Tigers declined an invitation to play in the NIT.
"We are happy about the development that transpired during his time here and think he will continue to make great strides as he transitions into the NBA," Jones said.
Simmons entered the season as the top freshman in the country and was the only player to average more than 19 points, 11 rebounds and four assists this season.
According to numerous NBA executives, Simmons is expected to be taken first or second in the NBA draft on June 23. Duke freshman Brandon Ingram, according to several NBA executives, has closed the gap, but the majority told ESPN they would still tab Simmons with the top pick.
"Ben was a tremendous teammate and a great competitor," Jones said. "He brought a great deal of excitement and enthusiasm to our team and did an outstanding job of making those around him better. That's something that this team will benefit from as we go forward."
Opposing coaches and NBA scouts have gushed over Simmons' all-court game, vision and instincts, as well as his exceptional ball-handling and passing ability for a player his height. However, Simmons wasn't immune to criticism. He never demonstrated that he could make jump shots consistently, rarely shot from outside and went only 1-of-3 from 3-point range all season. Also, he exhibited an inclination to pass rather than create his own shot in the late stages of close games.
Simmons' presence raised LSU's national exposure on television and filled seats in the stands. LSU averaged crowds of 11,400 at home and 13,700 on the road.
Even so, Simmons was not able to improve his college's fortunes on the court. After making the NCAA tournament the season before Simmons arrived, the Tigers missed the tourney while failing to reach 20 victories for the first time in three years.
LSU might have had a chance to reach the 20-victory mark in a postseason tournament such as the NIT, but Jones announced preemptively that the Tigers would not accept any invitations to postseason tournaments after they failed to receive a bid to the NCAA Tournament.
It remains to be seen whether Simmons will leave LSU in good academic standing. LSU was informed earlier this month that Simmons did not meet the requirements for the Wooden Award, which is presented to the nation's top college player. The award's published criteria say candidates must be full-time students, with consideration "given to scholastic achievement and aspirations." Candidates must have cumulative grade point averages of 2.0.
Simmons didn't start a Feb. 20 loss at Tennessee for what Jones said was an academic issue. While Simmons remains eligible for other national awards, Jones did not say in his end-of-season meeting with reporters last week whether Simmons was still going to class.
Information from ESPN's Jeff Goodman and The Associated Press was used in this report.