Williams made the announcement in a statement posted on Twitter.
"Words can't describe how blessed I am to be in this position," Williams wrote as part of his post. "... To my teammates, thank you for being more than just teammates. The love, support, and authenticity we show one another has honestly made this season a dream come true. The entire year has been filled with moments I will truly never forget."
"for I know the plans I have for you," declares the Lord † pic.twitter.com/G27wKAxJzq— Patrick Williams † (@patricklw4) March 26, 2020
The 6-foot-8, 225-pound Williams averaged 9.2 points and 4.0 rebounds in his freshman season.
He is the 20th-ranked prospect in ESPN's draft prospect rankings.
Williams is the second FSU player to declare his eligibility for the draft. Sophomore guard Devin Vassell, who led the Seminoles with 12.7 points per game this season, also has said he'd enter the draft.
The NBA draft is scheduled for June 25, but following worldwide suspensions of basketball activities amid the coronavirus outbreak, NBA front-office executives and others in the industry told ESPN they are bracing for the potential impact of a delayed 2020 draft with a heavily reduced pre-draft process.