The left-back, 26, was an eye-catching addition last August having made the switch from Italian giants Juventus in his homeland for an undisclosed nominal fee.
He was handed a three-year contract but departs the Baggies as a free agent two days on from a year later - with two more years still to run on his deal.
Frabotta exits The Hawthorns having made just seven first-team appearances.
Six of them were as a substitute in the Championship, where he did not start a single match. His last outing from the bench was on New Year's Day at home against Preston.
Frabotta's sole start for the club was in last August's miserable EFL Cup first round exit at League Two Fleetwood, shortly after his arrival.
He initially played second-fiddle briefly to Torbjorn Heggem, who then moved into his natural centre-back role. Callum Styles, another recruit from last summer, then made the left-back role his own despite very minimal experience in the position.
Frabotta has remained on the very fringes throughout his time at the club and often failed to make the matchday squad in the second half of last season.
He did not appear to be making inroads this summer under new head coach Ryan Mason either, having only played bit-parts as a late substitute in Albion's pre-season friendlies. New signing George Campbell, a right-sided centre-back, has been preferred as a sub left-back in recent weeks.
Albion are expected to be looking into moves for left-back cover and competition this month.