The 18-year-old Nigerian, who turns 19 later this month, has been widely regarded as one of the most exciting young prospects in Europe after impressing in Sweden’s top division this season.
Brighton moved quickly to secure his signature following a breakthrough campaign that highlighted his creativity and attacking potential.
“I’m looking forward to working with Zadok. Having seen his games and his attributes, he is a player that can impact games in the final third,” said manager Fabian Hurzeler.
“He’s still young, and will need time to adapt to the club and Premier League, but he’s an exciting player to watch and he brings the kind of creativity we know our fans will enjoy.
“He’s dynamic, has pace and likes to take players on. His attributes and ability will be a real addition to our attacking options.”