In the list of New Zealand rugby union teams (which does not include women's teams, local club or school teams, inactive teams, or non-geographic representative teams), Thames Valley and Waikato were the two teams from the North Island unions which were both formed in 1921.
The list does not include women's teams, local club or school teams, inactive teams, such as the North and South Island teams, or non-geographic representative teams, such as the New Zealand Universities, Marist, or Barbarians sides. Thames Valley 1921 Waikato 1921 
