An attacking midfielder, the 29-year-old returned to Farnborough for his third stint with the Evo-Stik League South East club in February 2017 on loan from then-National League South side Margate.
Donnelly previously plied his trade with Queens Park Rangers, Wealdstone, Aldershot Town, Swansea City, Newport County and Havant & Waterlooville.
Chippenham manager Mark Collier said: “Scott joins us with a wealth of experience. He will add a real quality to the squad. Scott had numerous options, however, he was impressed with the club’s vision and ambition”.
(Photo: Don Blandford)