Detectives are questioning a man following the fatal stabbing of a woman in Sydney's southwest.

The victim, aged in her 40s, was found by police and paramedics who were called to a residence in Alexander Crescent at Macquarie Fields about 5.15pm (AEDT) on Sunday.

She had sustained a number of stab wounds.

A 47-year-old man has been arrested and is assisting with inquiries into the attack, which police believe is domestic-related.

A crime scene has been established at the premises.