The news was confirmed this morning, a little more than 12 hours after the Shrimps had given the Northern Irishman permission to speak with the Scottish top flight club.
Also departing is assistant boss, Diarmuid O’Carroll, with goalkeeping coach Barry Roche taking charge for tonight’s trip to Rotherham United.
It will be his second stint as caretaker boss, having jointly filled the role with Kevin Ellison between the departure of Jim Bentley and arrival of Derek Adams in 2019.
“This comes after the club gave St Mirren permission to speak to Stephen on Monday 21 February.
“Assistant manager Diarmuid O’Carroll also departs and will join Stephen at the cinch Premiership side.
“We would like to thank Stephen and Diarmuid for their work since joining the club in June 2021.
“Barry Roche will take charge of Tuesday night’s game against Rotherham United, with the process of appointing a new manager now underway.”
With Jim Harvey, Sammy McIlroy and Bentley having spent a combined 25 years in the managerial role from 1994-2019, Robinson’s exit leaves the Shrimps seeking a third boss in as many years.
Robinson was only a quarter of the way through the three-year deal he had signed when succeeding Adams at the Mazuma Stadium last June.
He took charge of 40 competitive games which yielded 10 wins, nine draws and 21 defeats.
That included a second consecutive appearance in the FA Cup third round but his departure comes with the club fourth-bottom of the table and trying to avoid a first relegation in their history.
It’s understood that Martin Foyle, the club’s head of recruitment brought to the club by Robinson late last year, remains with the Shrimps.
Robinson told St Mirren’s official website: “It’s an absolute honour that St Mirren have come in and were willing to pay the compensation.
“It came out of the blue and when I spoke to the guys at the club it really impressed me what they are trying to do.
“We spoke in depth about where we can take the club and there’s real exciting times ahead. With the foundations that have already been built by Jim (Goodwin) it’s up to me to take them on and build on what’s already been done.”
St Mirren chief executive Tony Fitzpatrick said: “We are all delighted to welcome Stephen as the new manager of St Mirren. Stephen fits the profile of what we are looking for in a manager.
“He has great experience of the Scottish game and had good success on the park with Motherwell which saw him reach the finals of both the League and Scottish Cups as well a third-place finish and qualification for the Europa League.
“Stephen also did a tremendous job of developing young players at Motherwell which was an important consideration for us with the St Mirren Youth Academy, one of the main pillars of our football club.
“We would like to thank Morecambe FC for their co-operation in getting this deal completed.”
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