Ritter has previously played for FC Basel and FC Winterthur.
Jets coach Gary van Egmond welcomed Ritter to the club.
"Dominik can play as fullback, which is his preferred position, or a left-side stopper," van Egmond said.
"He has a lot of pace, he will suit our style of play and we will have good competition for spots in the backs.
"He is at a good age to be coming here, he has his best years ahead of him and we look forward to welcoming him to Newcastle and having him at the Jets."