Martinelli joins the club from Székesfehérvár of the Austrian Hockey League.
He previously had spells with the OHL’s London Knights and the University of Western Ontario, in addition to playing for Valpellice of Italy and Rosenborg in Norway.
“I’ve been in contact with Steve Thornton since the Continental Cup in 2014 when I played against the Giants (for Fischtown Pinguins of Bremerhaven) and he has been keen on having me in Belfast,” he said.
“I’m glad we kept in contact over the last couple of years and I finally have decided to make the switch and see what all the fuss is about.
“I’ve known Mitch Ganzak (played for the Giants last season) for a long time. He’s a former teammate of mine in Italy – I trust his opinions and he had nothing but great things to say about what the Giants had to offer.”
Steve Thornton, Giants’ Head of Hockey Operations, said: “Ryan is a big guy who clears the net really well.
“He is a winner, who won in Bremerhaven, and is a great skater as well. We wanted more size without sacrificing speed so he is the perfect guy for that job.
“I think the Giants fans will really like Ryan as he is a big guy who plays hard and takes away time and space.”
“He is mean in front of the net and is also a really good player. We are excited to have him.”