An Irish national is due to face court charged with the murder of a man reported to be her fiance after he was fatally stabbed in the neck in a fight at a home in Sydney's southwest.

The 29-year-old man, also an Irish national, died at the Padstow property early on Saturday, and the woman, 26, who lives at the home was arrested along with a 36-year-old man.

Police say the fight broke out after a man turned up at the property while three women and another man were there.

The Seven Network reported that the accused woman and the victim were engaged.

The woman was charged on Saturday afternoon with murder and was refused bail to face Parramatta Local Court on Sunday.

The 36-year-old man, of Revesby, was still assisting police with inquiries on Saturday night.

© AAP 2017