Jaouen has signed a four-year contract running until June 2030. The base fee is understood to be in the region of £18.5 million, with add-ons taking the potential total to £24 million.
The 6ft 6in stopper kept 15 clean sheets in 34 Ligue 2 appearances for Reims last season and has drawn comparisons with some of France's best young goalkeepers. He was born in Paris but moved to Brittany at the age of five and developed through the academy at En Avant Guingamp before joining Reims in 2023.
He spent the second half of the 2023-24 season on loan at Rodez, then the entirety of 2024-25 at USL Dunkerque, where his squad reached the Coupe de France semi-finals before losing to eventual winners Paris Saint-Germain.
Jaouen was full of warmth about his decision to move to Tyneside.
"I'm really excited to become a Newcastle United player. When I visited the training ground, I could see how passionate everyone is about the club and the work they do, and I loved the environment straight away. I also had the chance to see the stadium and it's huge."
He spoke directly about the supporter culture that has made the club famous.
"I've heard so much about the supporters and how they are the best in the country. The passion of the entire city and the atmosphere at St James' Park are famous throughout football, and I can't wait to experience that for myself and become a true Geordie."
He described his style as that of a modern goalkeeper comfortable on the ball.
"As a goalkeeper, I enjoy one on one situations and playing as a modern keeper, building from the back and being comfortable with the ball at my feet. Now I want to develop alongside the amazing players and staff here, enjoy my football, and prove my value on the pitch."
Newcastle United manager Eddie Howe was direct in his enthusiasm for the signing.
"Ewen is a great addition and I am delighted to welcome him to Newcastle United. He is an exciting young goalkeeper who has shown real promise during his time in France. He has a calmness and presence that belies his age, and he's someone we feel can grow and improve within our environment."
Sporting director Ross Wilson confirmed the club had been working on the deal for several months.
"Ewen is a hugely talented young goalkeeper who has gained a lot of admirers across European clubs. What stood out for us, in all of our discussions, was his ambition, his focus and his determination to be here."
Jaouen becomes Newcastle's first signing of the summer and arrives into a goalkeeping department in transition. Aaron Ramsdale's loan from Southampton has ended, with Newcastle opting against making it permanent. John Ruddy and Odysseas Vlachodimos are also set to depart.
Nick Pope remains at the club but has been told he can leave if a suitable offer arrives. Jaouen may not simply be the backup.