James John Rantz (born February 24, 1938, at Saint Paul, Minnesota) is an American former professional baseball player and executive.
Cloud Rox, the Twins' affiliate in the Class A Northern League, for one season (1965), he moved into the club's front office in 1965.
Other than a one-year stint in 1977 as manager of the Wisconsin Rapids Twins of the Class A Midwest League, Rantz worked for Brophy for the next 16 years.
Following Brophy's retirement from the Twins in 1985 due to health problems, Rantz was promoted to succeed him as Director of Minor League Operations.
In recognition of his accomplishments as the team's player development boss for 22 years, Rantz was inducted into the Minnesota Twins Hall of Fame in 2007.