The incident happened around 10:30 p.m. Monday on Salisbury Park Drive in the vicinity of St. Paul's Street in Westbury.
Nassau County police say a 22-year-old man driving a 2011 BMW sedan was driving north when he crossed into the southbound lane, colliding head-on with a 2013 BMW SUV driven by 51-year-old Maria Duarte.
She was rushed to an area hospital, where she was pronounced dead.
The man, who had to be extricated from his vehicle, was hospitalized in serious condition.
Both vehicles were impounded for brake and safety checks.
The investigation is ongoing.