Forbes says Ms Parry-Okeden, who grew up in Hawaii and moved to her ex-husband's country of birth Australia decades ago, was recently confirmed to be an Australian citizen.

Gina Rinehart. Credit:Lisa Maree Williams

After her mother's 2007, death she inherited a quarter of US media conglomerate Cox Enterprises, America's third-biggest cable TV company.

This is not the first time Forbes has named Ms Parry-Okeden as Australia's richest person. She first took the title in 2009, overtaking mining magnate Andrew "Twiggy" Forrest for the top spot

Forbes says Ms Rinehart's wealth has slipped $US3.2 billion in the past year, mainly due to falling iron ore prices and a legal ruling which impacted her shareholding in Hancock Prospecting.