The woman, aged 38, was found dead in the kitchen of her Quakers Hill home in northwest Sydney with multiple stab wounds on Sunday.
NSW police had been called to the home on Illabo St just before 5am following reports of a disturbance.
A 30-year-old man was found on the footpath outside the home with stab wounds to his stomach and hands.
He died about 9am at Liverpool Hospital after being rushed there in a critical condition.
Police charged a 47-year-old man with two counts of murder on Sunday evening after he attended Blacktown Police Station earlier that morning.
He is set to face the Bail Division Court on Monday.
No one else was home at the time of the incident.
The victims were believed to have been in a relationship, Superintendent Jason Joyce said.
"We're not sure what type of relationship or the duration of that relationship," he told reporters.
"The male that's in custody was previously in a relationship with the female."
Supt Joyce said the incident appeared to be domestic violence-related, based on early inquiries.
"Obviously this is a very traumatic incident, traumatic for my police. My condolences go out to the families of the deceased involved," Supt Joyce said.
Multiple crime scenes were established, including at the home where the couple were killed, the arrested man's Blacktown home, and at the hospital.
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