The Dutch midfielder has established himself as a key member of the squad since joining the club from PSV Eindhoven in August 2017.
Head Coach Graham Potter said, “I’m delighted Davy has agreed this new contract which he fully deserves.
“I was aware of his contribution in our first two years in the Premier League and since I came to the club, he has shown his qualities both on and off the pitch on a consistent basis.
“He is a great professional who is always looking to improve every aspect of his game and I’m really pleased that he is going to be part of our journey going forward.”
In Albion’s first season in the Premier League he made 43 appearances. This season he has already featured 26 times and netted in the 2-2 draw against Wolves in December.
It is shaping up to be a big year for Propper, who is hoping to be part of the Netherlands squad for this summer’s European Championships.
He has won 19 caps and scored three goals since making his debut in 2015 and was part of the squad that finished runners-up in the Nations League last year. Propper began his professional career with Vitesse before moving to PSV in 2015.