G.L. c. 208, § 6
Venue of libel
Actions for divorce shall be filed, heard and determined in the probate court, held for the county where one of the parties lives, except that if either party still resides in the county where the parties last lived together, the action shall be heard and determined in a court for that county. In the event of hardship or inconvenience to either party, the court having jurisdiction may transfer such action for hearing to a court in a county in which such party resides.