One lucky West Australian has scooped up the entire $20 million Lotto Powerball Division 1 prize.

It is the fourth-largest Lotto prize ever won in the state and the third Division 1 Powerball win in WA this year.

The record for the state's largest Lotto win sits at $30 million, which was won in 2001 and 2007.

"We are thrilled that luck has struck and we have a multi-million dollar winner somewhere in our state," Lotterywest's Pina Compagnone said.

The winning ticket was reportedly sold at a newsagency in Perth's southern suburbs.