Alexander Ronald McDonnell was an American politician and banker. A Republican member of the Montana Legislature. He was elected to the Montana Senate in 1953 to represent Senate District 19, which at the time included Sweet Grass County and Park County. McDonnell served four consecutive terms as a Senator, retiring from the role in 1969. McDonnell also served as the Chairman of Citizens Bank & Trust Co, a bank which his father, Charles McDonnell had started.