Police are calling for sightings of Elizabeth Wielga, who was last seen in the Tongariro area, while visiting from Australia.
Wielga, 67, did not show up for her flight home on 30 August, a police spokesperson said in a statement.
They were alerted by Wielga's family when she did not return home when expected: "her family is concerned for her welfare".
It is believed the missing woman checked out of accommodation in Tongariro earlier that day.
"While our enquiries are in their early stages, at this point Police have not been able to establish Ms Weilga's movements after she left her accommodation," the police spokesperson said.
Police want to hear from anyone who had seen her, or had any information to help them find her: "we urge you to get in touch", they said.
Information can be supplied by calling 105 and quoting file number 200905/7641.