Kāti Mamoe, or Ngāti Mamoe, is an historic Māoriiwi. Originally from the Heretaunga (Hastings) area they moved in the 16th century to the South Island which at the time was occupied by Waitaha.
Kāti Mamoe were largely subsequently absorbed via marriage and conquest by Ngāi Tahu who migrated south a century later. There is no distinct Kāti Mamoe organisation today but many Ngāi Tahu have Kāti Mamoe links in their whakapapa. In the far south of the island especially, "... southern Māori still think of themselves as Ngai Tahu-Ngati Mamoe, a synthesis of the two tribal groups ...."