The Ao Nagas are a major Naga ethnic group native to Mokokchung District of Nagaland, Northeast India. Their main territory is from Tsula (Dikhu) Valley in the east to Tsurang (Disai) Valley in the west in Mokokchung district.
The Ao Nagas refer to themselves as Aoer, which means "those who came" from across the Dikhu river.
They were the first Nagas to embrace Christianity and by virtue of this development the Aos availed themselves of the Western education that came along with Christianity. In the process the Aos pioneered among the Nagas in many fields. Christianity first entered into the Ao territory when an American Baptist missionary, Edwin W. Clark, reached an Ao village called Molungkimong in 1872.