The goalkeeper had initially been on loan at the north east club from Sparta Prague, but he has now signed a permanent deal that will see him stay at St James' Park.
The 29-year-old was a key part of Newcastle's season, with his debut against Manchester United particularly memorable, as the 'Magpies' finished 10th in the league.
Manager Rafa Benítez said: "We’re delighted to finalise the permanent signing of Martin to Newcastle United today.
"Ever since he arrived with us on loan he has shown a fantastic attitude and great work ethic, and of course we have been very impressed with his performances for us on the pitch last season.
"This was one of the key positions we had identified we needed to strengthen and had been concerned about, so it is excellent news that we are able now to sign him on a permanent basis.
"The loan deal with an option to buy was the perfect deal for the club."
Dubravka has 10 caps for Slovakia, and has signed a four year deal with Newcastle.
30 May 2018