John Alexander Mathieson (May 19, 1863 – January 7, 1947) was a Prince Edward Island politician and jurist, the 12th premier. Mathieson was born in Harrington and was a graduate of Prince of Wales College. He was a schoolmaster and lawyer before entering politics with his election to the province's legislature as a Conservative in 1900. He represented the district of 4th Kings in his first term in the legislature, then shifted to 5th Kings in 1904. In 1917, Premier Mathieson left politics to accept an appointment as Chief Justice and served in that position until he retired in 1943.