The Moroccan international joins Conor Coady and Matt Doherty in recently agreeing new terms at the club, who sit seventh in the Premier League table with 39 points.
The 28-year-old has made 18 appearances so far this season, scoring twice - in the away draw with Fulham on Boxing Day and home win over West Ham at the end of January.
“I’m very happy to sign a new deal with this club. It was very important for me because since the new owners bought the club, I’m here to have a big part in this project." he said.
“I came here to try to help the club get into the Premier League, we achieved that, and now we have to continue in this way, to help the club to grow every year to become a very big club in England. I’m very happy to have a part in this big project.
“I’ve been here three years now, so everything is good for me and my family. We like living in England, we like living here, playing at this club, in this stadium, with these fans, so everything is fantastic and is good for me.”
Saiss played a key role in Wolves' promotion from the Championship last season, making 44 appearances across all competitions as they romped to the title.
He originally joined Wolves from French side Angers in the summer of 2016, signing after the appointment of Walter Zenga for an undisclosed fee.
“I remember when I signed here, the first season was very hard. We changed the coach two or three times and it was not very easy for me because it was my first experience in a new country." he said, regarding his time at the club.
"But after the second season it was fantastic, because we got promotion, we won the title, and I played my first World Cup with my national team, so everything was fantastic last season.
“This season is totally new for a big part of the squad, because nobody has played in the Premier League. It was hard at the beginning because I didn’t play a lot, I came back late from World Cup and everything was new for me.
“But even though I didn’t play a lot, it was a good experience to learn but I try to stay focused and do everything in training and be ready for when the coach calls me to play.
“When he did it, I think I tried to do my best to show to the coach, and the club, that I am here and I can help the team.”