The Onondaga (Onundagaono or the People of the Hills) are one of the original five constituent tribes of the League of the Iroquois (Hodenosaunee). Their traditional homeland is in and around Onondaga County, New York. Being centrally located, they were the keepers of the fire in the figurative longhouse, with the Cayuga and Seneca to their west and the Oneida and Mohawk to their east. For this reason, the League of the Iroquois historically met at Onondaga, as indeed the traditional chiefs do today.

In the American Revolutionary War, the Onondaga were at first officially neutral, although individual Onondaga warriors were involved in at least one raid on American settlements. The Onondaga later sided with the majority of the League and fought against the United States in alliance with the British Crown, after an American attack on their main village on April 20, 1779. Many Onondaga therefore followed Joseph Brant to Six Nations, Ontario after the United States was accorded independence. Those remaining in New York are under the government of traditional chiefs nominated by matriarchs, rather than elected.

On November 11, 1794, the Onondaga Nation (along with the other Haudenosaunee nations) signed the Treaty of Canandaigua with the United States.

On March 11, 2005, the Onondaga Nation of Nedrow, New York, filed a land rights action in federal court, seeking acknowledgement of title to over 3,000 square miles of ancestral lands centering on Syracuse, New York, as well as increased influence over environmental restoration efforts at Onondaga Lake and other EPA Superfund sites.

Onondaga bands today

• Onondaga Nation in Nedrow, New York outside Syracuse
• Onondaga Clear Sky and Bearfoot Onondaga , both at Six Nations of the Grand River

Other spellings encountered

• Onoda'gega
• Onontakeka
• Onondagaono