The 28-year-old forward joins Hull City on a two-year deal for an undisclosed fee, with the Club holding an option of adding a further year.
Magennis, a Northern Ireland international, came through Cardiff City’s youth system before moving to Scotland to join Aberdeen. His best spells to date came with Kilmarnock and then Charlton Athletic, while his 2018/19 season with Bolton brought seven goals.
He has earned more than 40 caps for Northern Ireland, with six goals to his name, and represented his country at Euro 2016.
Speaking about the signing of Magennis, Head Coach Grant McCann said: “Josh’s career has gone from strength to strength and he is a proven international footballer. He can play anywhere across the front three and he is a versatile forward.
“He’s strong, direct and quick and he will add strong competition and physicality to us.”