The left wing for Quebec Major Junior League's Rimouski was named the MVP of this year's world junior championships and last season scored 35 goals and 77 assists (112 points) in 52 games.
"I'm really excited to join the New York Rangers," Lafreniere said after being selected first in the draft, which was held virtually due to coronavirus concerns.
"I can't wait to see the fans. I've heard a lot of good things about the fans and about the building," he said.
"I'm really honored."
Los Angeles Kings selected center Quinton Byfield with the second pick, before the Ottawa Senators chose center Tim Stutzle. Stutzle's selection was announced by Jeopardy! host and University of Ottawa graduate Alex Trebek.
The Rangers won the first overall pick after being one of eight teams that failed to advance past the qualifying round of the Stanley Cup playoffs in this year's coronavirus-interrupted season.
"We've had a few [Zoom calls] with him, obviously we've done our homework on him, we've talked to a lot of people around him," Rangers general manager Jeff Gorton said this week, according to NHL.com.
"He's a really humble kid that gives credit to everybody around him. He's a good family kid. He works really hard. He's really focused."
Lafreniere will join winger Kaapo Kakko, who the Rangers selected with the No. 2 pick in last year's draft, 24-year-old goalie Igor Shesterkin and the league's top rookie in the 2015-16 season, winger Artemi Panarin.
(Reporting by Rory Carroll in Los Angeles; editing by Richard Pullin)