Joan Withers has been named the country's top woman of influence.

The chair of Mighty River Power and TVNZ, director of ANZ and a member of the Treasury Advisory Board, was the Supreme Winner at the Women of Influence Awards held last night in Auckland.

She's also the former CEO of The Radio Network.

Judges said her work championing board diversity and striving to close the gender gap resulted in a unanimous decision.

Joan Withers began her career as a junior bank teller, rising to lead two NZX15 companies - the only woman to have achieved that to date.