Cumbria-born Guy had been told he was free to find a new club and had been training with Carlisle before reaching agreement with Saints to end his contract a year before it was due to expire.
A club statement read: "It has been confirmed this morning that Lewis Guy has cancelled his contract with St Mirren Football Club by mutual consent."
The 27-year-old joined St Mirren a year ago from MK Dons and hit six goals in 35 appearances.
His final appearance, in a goalless draw with Aberdeen in the penultimate match of the season, saw him substituted 16 minutes after coming on, following an exchange of words with assistant manager Tommy Craig.
- Sports & Recreation
- St Mirren Football Club
- Lewis Guy