St. Catherine of Siena Medical Center is a 296-bed,[1][2] not-for-profit hospital located on Long Island in Smithtown, New York.

[3][4] It is a major regional clinical campus for clinical clerkships and postgraduate medical training affiliated with the New York Institute of Technology College of Osteopathic Medicine, one of the largest medical schools in the United States.

Construction of the hospital began in 1962 on a 74-acre plot of land on the outskirts of Smithtown, Long Island, New York.

By its fifth year of operation, it had grown to 357 full-time employees and 151 part-time, and had provided services to nearly 100,000 patients.

A local Smithtown newspaper ran an article on the fifth anniversary of St. John's opening, celebrating the hospital's delivery of Suffolk County's millionth resident.