(May 6, 1899-May 28, 1989). The son of Otto N. Frenzel I and the nephew of John P. Frenzel II (See) and a native of Indianapolis, Frenzel attended Cornell University after graduating from . While a student at Cornell he enlisted in the Naval Reserve and served in the United States Navy during World War I. Returning to Indianapolis, Frenzel began his career in banking as a messenger boy in his father’s in 1919. Progressing through all offices, he served as the bank’s president from 1945 to 1966, chairman of the board from 1966 to 1969, and retired as chairman of the executive committee of Merchants National Bank and Trust Company two weeks before his death. He also served as president of the Indiana Bankers Association and as a member of the executive committee of the American Bankers Association.
Throughout his banking career, Frenzel was a director of many Indianapolis companies including, , , and American States Insurance. He also served as a director of the and Youngstown Sheet and Tube. From 1936 to 1945, Frenzel served as president of the Indiana Trust Company.
In civic service, Frenzel served as a director for a number of groups: the Indiana State Chamber of Commerce, Indianapolis Hospital Development Association, United Fund of Greater Indianapolis (), Indianapolis Civic Progress Association, and the Indianapolis . He was also a trustee of both Park School (see ) and . A member of the Traders Point Hunt Club, Frenzel served as its president from 1936 to 1938. During World War II, he served on the War Finance Committee, and in 1954 he was appointed to a four-year term as chairman of the Indiana Toll Bridge Commission.
In recognition of his many civic contributions, Frenzel was awarded an honorary Doctor of Laws degree from Indiana Central College () in 1965.