The Guelph Biltmore Mad Hatters were a Canadian junior ice hockey team in the Ontario Hockey Association (OHA) from 1940 to 1942, and 1947 to 1960. The team was often known as the "Biltmores" and sponsored by the Guelph Biltmore Hat Company, and played home games at the Guelph Memorial Gardens.

The Guelph Biltmore Mad Hatters were a brief note in junior hockey history, but left an impression on the game during 13 years of operation. The team that was sponsored by a local manufacturer in the Royal City would capture a national championship, several provincial titles, and send four men on to the Hockey Hall of Fame.

The team was founded as the Guelph Indians for the 1936-37 season. After four seasons, the Guelph Biltmore Hat Company became the team's sponsors. After two more seasons of play, the team was put on hiatus for World War II. The team was resurrected in 1947 as a farm team for the New York Rangers of the NHL and coached by former Rangers forward Alf Pike until the end of 1954. Eddie Bush, a former NHL defenceman, would take over the coaching duties from 1954 onwards.

The Biltmore Hat Company rewarded any player scoring three or more goals in one game the choice of hats at their factory, bringing new meaning to the term "hat trick."

After running into financial trouble in 1960, new ownership renamed the team the Guelph Royals, after the city's nickname. Three years later the team moved becoming the Kitchener Rangers, taking the name of the parent club from the NHL.

Four alumni of the Mad Hatters have been inducted into the Hockey Hall of Fame: Andy Bathgate, Rod Gilbert, Harry Howell and Jean Ratelle. Players who also had impressive NHL careers are Dean Prentice and Ron Murphy.

Played as Guelph Indians, 1936-40.