The 25-year-old striker heads to the Premier League after a prolific two- and a-bit seasons in Belgium, scoring 41 goals in his 82 games.
David featured in four of Canada's five World Cup fixtures this summer, coming on as a substitute in all of them, scoring in the 2-1 group stage defeat to Switzerland.
He has now been confirmed as Brighton’s latest addition, joining on an initial loan with an obligation to buy for £22million should certain criteria be met.
"Promise is someone we have been watching for some time, he is an out-and-out striker who possesses outstanding physical attributes and a track record of scoring goals," said sporting director Mike Cave.
"His experience at international level and in European competition will hopefully prove valuable this season.
"At 25, he's entering his prime playing years and we're excited to see him continue to develop in our environment."