Ms Armstrong (pictured) most recently acted as the NSW Treasury’s first general counsel, providing the government with advice on developing electricity network legislation and the long-term leasing of the state's three largest ports.
She spent 18 years at the Crown Solicitor’s Office (CSO), previously acting as general counsel and as an assistant crown solicitor in commercial and administrative law.
Before joining the CSO in 1995, Ms Armstrong had a stint at a major commercial law firm and spent a year working as an associate for the now-retired High Court judge, Michael McHugh.
The announcement follows hot on the heels of two other glass ceiling-breaking appointments; Gladys Berejiklian recently stepped up as the first female treasurer of NSW and Gabrielle Upton became the state's first female attorney-general in April.
“I am extremely honoured to be the first female Crown Solicitor in NSW, particularly as I am following in the footsteps of the state's first female attorney-general and treasurer," Ms Armstrong said.
“It is incredibly important for female lawyers and women in government to have positive role models who hold senior positions in the public service.
“There is no doubt it will be a huge challenge, but an exciting and rewarding one and I look forward to working broadly across the legal and government sectors over coming months."
In making the appointment, Ms Upton described Ms Armstrong as “an outstanding solicitor with 23 years' experience in government and commercial law”.
Ms Armstrong replaces Ian Knight, who retired in February, and starts on 13 July