The striker moves to the club on a two-year deal with the Whites having a long-held interest in the Northern Ireland international.
Starting his senior career with Cardiff City, the 27-year-old spent time on loan with Grimsby Town before moving north of the border to sign for Aberdeen in July 2010.
Joining Kilmarnock in July 2014 following a temporary stint with St Mirren, he scored 20 goals in his two seasons at Rugby Park.
Boasting nearly 40 international caps, Magennis scored his first goal for his country in Northern Ireland’s 3-1 victory over Greece to book their place for Euro 2016 before featuring three times at the finals in France.
Signing for Charlton in August 2016 following the tournament, he recorded double figures in both of his campaigns at The Valley and now links up with Bolton prior to this weekend’s Sky Bet Championship opener against West Bromwich Albion.
Speaking to bwfc.co.uk following the switch, Magennis said: "It's a massive move for myself and when I found out about the club's initial interest, I was itching to get here.
"I'm absolutely delighted to be a Bolton Wanderers player though and hopefully we can make this season a successful one."
Manager Phil Parkinson added: “I’ve been looking to add to our strike force and I’m delighted to have brought in Josh.
"He’s got a real desire and hunger, and I'm looking forward to working with him.”
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