The 20-year-old forward also becomes the most expensive Canadian player ever following the transfer, obliterating the €11.3-million sum that Bayern Munich paid to acquire Alphonso Davies from the Vancouver Whitecaps.
"I want to play and to progress, and I think that this is the perfect place," David said after inking a five-year contract. "I'm a player who knows his place on the pitch. I love to play to my qualities, notably with speed and technique. I'm also eager to see our fans! Let's go LOSC!"
David's move to France follows an 18-goal campaign in Belgium's top tier and three additional strikes on Europa League duty. His signing is designed to compensate for the departure of Victor Osimhen, who joined Napoli last month for an initial €50-million fee.
The Ottawa-raised star also attracted interest from Premier League clubs Leeds United and Arsenal, according to The Canadian Press.
"He is a player with not only great physical and technical abilities, but also mental qualities which make him particularly alert, agile, and decisive," said Lille chief executive Marc Ingla. "Jonathan is a very intelligent boy who I am sure will fit in with the LOSC style of play and the French championship.
"We thank him for choosing to join our project and wish him the best of luck in our jersey."
David has made 12 appearances for Canada, scoring 11 goals.