Williamson, who hails from Spartanburg, South Carolina, also had in-state schools South Carolina and Clemson among his top choices.
"Duke stood out because the brotherhood represents a family," Williamson said. "Coach K is just the most legendary coach that ever coached college basketball. I feel like going to Duke University, I can learn a lot from him."
Duke now has commitments from the three top-rated players in the ESPN 100, with No. 1 R.J. Barrett and No. 3 Cam Reddish joining Williamson in Durham. The Blue Devils also have the commitment of No. 10 Tre Jones.
Duke is the first team to get each of top three recruits in the same class in the ESPN 100 era (since 2007).
"I feel like we can all do something special," Williamson said.
Duke is expected to lose most, if not all, of its starting five after this season. Grayson Allen is a senior, while Marvin Bagley III, Wendell Carter Jr. and Trevon Duval are all projected first-round picks.
While Williamson's dunking ability and jaw-dropping athleticism are his best attributes, he's more than that. The 6-foot-6, 275-pound power forward is built like a tight end, but he combines that strength and physicality with quick feet and adept passing ability.
Williamson is still at his best in transition, though, and will need to get in better shape and improve his shooting ability to dominate at the next level.
Williamson has built a massive social media presence, with has 1.1 million Instagram followers, and close to 100,000 Twitter followers. Drake wore his jersey in an Instagram post.
"It's fun, and it can be not-so-fun at the same time," he previously has said of the attention. "It's fun because, going all over the world, I was in Italy and people were asking me for pictures, 'Are you Zion? I don't believe you're in Italy right now. This is crazy.' I tell [people] my name, and they go, 'Oh my god, it's really you.' That part's fun. People knowing who I am."
Williamson thanked both Clemson and South Carolina for their recruitments.
"I love my state to death," he said.
ESPN's Jeff Borzello contributed to this report.