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- Oglala Sioux Tribe
(previously listed as Oglala Sioux Tribe of the Pine Ridge Reservation, South Dakota) - Ohkay Owingeh, New Mexico
(formerly the Pueblo of San Juan) - Omaha Tribe of Nebraska
- Oneida Nation of New York
- Oneida Tribe of Indians of Wisconsin
- Onondaga Nation
(previously listed as Onondaga Nation of New York) - Otoe-Missouria Tribe of Indians, Oklahoma
- Ottawa Tribe of Oklahoma
Read more about this topic: Federally Recognized Tribes