Gladys Berejiklian has become the 45th Premier of New South Wales after being elected unopposed by the Liberal Party, The Daily Mail reports.

New South Wales is a state on the east coast of Australia, with Sydney as its state capital. In March 2014, the estimated population of New South Wales was 7.5 million, making it Australia's most populous state.

The daughter of Armenian migrants promised to go 'harder' than her predecessor Mike Baird as the state's first female Liberal premier.

This will make the treasurer the 45th premier of NSW, following Baird's surprise retirement from politics to be with his unwell sister Julia Baird, an ABC television presenter.

The party's chief whip Chris Patterson told a large media scrum Ms Berejiklian, 46, had been confirmed as the new leader, with 33-year-old father-of-four Dominic Perrottet her Liberal deputy.

Berejiklian will become the state's second female premier when she is sworn in on Monday afternoon and takes the government to the next election, which is being held in March 2019.