Goodwin averaged 14.0 points a game last season, amassing 448 points, 10th-most all time for a freshman at Kentucky.
"This is something I've dreamed about my entire life and I feel like the opportunity is there for me to play at the next level," said Goodwin. "I will stay in Lexington to finish my schoolwork this semester before continuing to pursue my dream.
"I've loved my time at UK and want to thank Coach Cal, the staff and my teammates for helping me get where I am. I especially want to thank the Big Blue Nation for all their support."
Kentucky Coach John Calipari said he "really wanted" Goodwin back for a sophomore season but he fully supported the player's decision to enter the draft.
Kentucky has been particularly hard-hit by players leaving well before their eligibility was complete. The Wildcats won the NCAA Tournament in 2012 but then lost all five starters -- including freshmen Anthony Davis, Michael Kidd-Gilchrist and Marquis Teague, and sophomores Doron Lamb and Terrence Jones -- when they players left last spring for the NBA.
Bucking that trend, freshman Willie Cauley-Stein and sophomore Kyle Wiltjer said they will return to Kentucky next season. Cauley-Stein, like Goodwin, was an all-SEC freshman team selection.