A former Wales 7s star with more than 100 international 7s games under his belt, Cross was part of the Great Britain Olympic 7s squad which claimed a silver medal at the Rio de Janeiro Games in 2016.
Playing 53 times for Ospreys in the URC, he has also appeared 14 times in European competition for the Welsh region.
Newcastle Falcons head coach Alex Codling welcomed the arrival of the versatile forward, saying: “Sam is a very dynamic back-rower who has played international rugby at both 7s and 15s.
“His explosive ability will very much suit the way we want to play, he’s a great fit for us and he can thrive in a number of positions right across the back row.”
Similarly enthusiastic about the move, Cross said: “I spoke to Alex earlier in the summer about his plans for Newcastle, which really excited me, and when you combine that with what he helped to achieve over at Oyonnax last season I was keen to link up with him.
“The opportunity to play in the Gallagher Premiership was also a big draw because I’ve loved watching it for years, and it’s a great product.
“Newcastle’s artificial pitch will suit me because I like a quick game, and I’m used to the cold with being from Brynmawr in the Welsh valleys!”
Arriving at Kingston Park during a period of change, he added: “It’s an exciting time for the Falcons, and it has that feel of a new era with some new coaches and a lot of new players coming in.
“Everyone’s gelling together to create that new culture and a new vibe around the place, and it’s an exciting crop of players with loads of young talent. I’ve been really impressed by a lot of the boys who have come through the academy, and it’ll be good to combine that with some of the more experienced guys.”
Cross said: “I like playing on the artificial pitch so that will really suit me, having a quality surface all year round, and I love a fast game.
“I’ll try and run some angles, pick some good lines, look to offload and get the ball to space, and with my sevens background that open-field running is something I’ll look to bring.
“Speaking to the coaches here they want to play a good brand of rugby, and that’s something that is important to me. To have the opportunity to do that up here at Newcastle is a really exciting prospect.”