Wolves have paid the Greek champions £6.85m for Sa’s signature.
The 28-year-old won two Greek titles in three seasons with Olympiacos after initially joining on loan from FC Porto in the summer of 2018.
He faced Wolves while with Olympiacos in the Europa League round of 16 stage in the 2019/2020 season.
Sa is Wolves’ new manager Bruno Lage’s fourth summer signing after Rayan Ait-Nouri, Francisco Trincao and Yerson Mosquera.
Wolves technical director Scott Sellars said: “Jose is somebody who is very much coming into his peak years as a goalkeeper and has always been high up on our target list.
“He’s aggressive when coming for crosses, he commands his penalty area, has excellent distribution and he’s a very pro-active goalkeeper, and will be an important part in how we want to play under Bruno.
“He’s also gained so much experience throughout his career, especially over the last few years while playing in Greece, appearing for Olympiacos in the Champions League and in the Europa League, where he played against us not so long ago.
“He’s played for Portugal, he’s won several league titles and we certainly feel he’s a keeper who is ready for that next step into the Premier League.”
Wolves begin their 2021/2022 Premier League campaign away at FA Cup holders Leicester City on August 14.
