John R. Plewa was a steelworker and a Democratic politician from Wisconsin.
Born in Milwaukee, Wisconsin, Plewa graduated from the University of Wisconsin–Whitewater.
In 1970, he was a candidate in a four-way primary which unseated incumbent state Senator Leland McParland, losing to Kurt Frank. In 1972, Plewa was elected to the Wisconsin State Assembly serving until 1984, when he was elected to the Wisconsin State Senate in a special election after incumbent Jerry Kleczka was elected to the Congressional seat long held by Clement Zablocki. The Lake Parkway of Wisconsin Highway 794 was named in memory of Senator Plewa.
He was a member of the Cudahy Junior Chamber of Commerce, and the United Steelworkers Union.