Kenneth Joseph "Ken" Donnelly (July 15, 1950 – April 2, 2017) was an American politician. He served as a member of the Massachusetts State Senate from 2009 until his death in 2017. He represented the Fourth Middlesex district. He was a Democrat.
Donnelly was born in Arlington, Massachusetts in 1950. He graduated from the University of Massachusetts Amherst with a BA in Labor Studies. He was a retired lieutenant with the Lexington Fire Department in Lexington, Massachusetts.
Donnelly died on April 2, 2017 in Arlington, Massachusetts from complications of a brain tumor, aged 66.