The 20-year-old woman was reported missing to Wanaka police yesterday and a search operation was launched, Acting Senior Sergeant Ian Temple, of the Southern District Command Centre, said.
The woman was part of a larger group - believed to be an educational group from the United States - travelling through the Gillespie Pass area, between Young Valley and Wilkin Valley.
She was last seen about 3pm on Saturday.
An aircraft is also being used in the search.
The Department of Conservation describes the Gillespie Pass Circuit as a 58km, three to four day round trip, suitable outside the winter months for relatively experienced parties.