Dame Tariana Turia and Turama Hawira have been appointed to the office of Te Pou Tupua.
The pair will act as the human face of Te Awa Tupua, the legal personhood of the Whanganui River, for the next three years.
The river's legal status was established earlier this year by the Te Awa Tupua (Whanganui River Claims Settlement) Act.
Te Pou Tupua - a singular role which represents neither the Crown nor iwi - will speak on behalf of Te Awa Tupua and uphold its four values.
Those are that the river is a source of physical and spiritual sustenance, that it runs from the mountain to the sea and is indivisible, that iwi and hapu have an inalienable relationship with the river and that large streams flow into one another and form one river.
Te Pou Tupua will also administer a $30 million contestable fund which will be available to support initiatives relating to the environmental enhancement of Te Awa Tupua.
Mr Hawira has been a trustee and director of several hapu and iwi trusts and organisations, including chairing the Nga Rauru Iwi post settlement governance entity.
He is a director of the Morikaunui Incorporation which farms large tracts of Maori owned land and is fluent in the Whanganui dialect.
Dame Tariana was an MP from 1996 until 2014 including time as the Minister for Whānau Ora, Disability Issues and the Community and Voluntary Sector.
Dame Tariana is of Ngāti Apa, Ngā Wairiki, Ngā Rauru, Tuwharetoa and Whanganui.
Gerrard Albert, chairman of the post-settlement governance entity for Whanganui iwi, Ngā Tāngata Tiaki o Whanganui, said he was pleased with the co-operation amongst all iwi with interests in the Whanganui River.
"The role of Te Pou Tupua as the human face of Te Awa Tupua is of great importance to the new framework that has been created for the Whanganui River.
"Te Pou Tupua will be engaging actively with the iwi, hapū and communities of the Whanganui River, local government and the other groups as part of its work."