The 28-year-old defender joined Saints from Southend in July 2020.
Captain Joe Shaughnessy has signed a new two-year deal with St Mirren after enjoying a “brilliant” debut season with the Buddies.
The 28-year-old defender joined Saints from Southend in July 2020 and was named as vice-captain in October before becoming skipper in January.
Shaughnessy, now tied to the Paisley club until 2023, helped St Mirren finish in the highest top-flight position since 1989 (seventh) and reached the semi-finals of both the Betfred Cup and Scottish Cup for the first time since 1981/82.
The Irishman told stmirren.com: “It’s something I wanted to get done in the last couple of months and I’m really happy it’s been done.
“It’s been brilliant.
“I thought when I signed that we were building a good squad to have a good season and it turned out to be that.
“I really enjoyed it and that’s why I’m really pleased to get signed up for another two years.
“We nearly achieved everything that we set out for at the start of the season.
“We came really close to finishing top six and reached two semi-finals.
“Everyone at the club wants to kick on and make sure next season is as good, if not better, than last season.”
St Mirren manager Jim Goodwin said: “Joe is our captain and he’s been a great leader for us since he joined.
“He has been a good senior pro for us and really led by example in his time at the club.
“He’s a great role model for some of our younger players and we’re pleased that he has agreed to extend his time at the club.”