Saint Mary's Hospital (abbreviated STMH) is a Yale-affiliated^[2] urban hospital located at 56 Franklin Street, Waterbury, Connecticut. Operated by Trinity Health, it was founded in 1907 by the Sisters of Saint Joseph of Chambéry and is designated as a Level II trauma center. Saint Mary's has been a teaching hospital for the Yale University School of Medicine for over 40 years.^[3]

In 2011, Waterbury Hospital and St. Mary's Hospital said they planned on merging.^[4] The merger between St. Mary's Hospital and Waterbury Hospital was called off in 2012.^[5]

In July 2014 Tenet Healthcare announced that the hospital would be acquired by a Tenet subsidiary, with the hospital's religious directives and uncompensated care policies remaining intact. Tenet was chosen by the hospital after a four-year selection process.^[6] The Tenet deal unraveled in 2015 when Tenet expressed concern with the conditions on the sale set by the state of Connecticut.^[7]

In September 2015, Saint Mary's Hospital was acquired by Livonia, Michigan-based Trinity Health, who had recently acquired Saint Francis Hospital & Medical Center in Hartford.^[8] In 2018, Trinity Health opened a center for multiple sclerosis treatment and research at the hospital.^[9]

The HealthGrades website contains quality data for St. Mary's Hospital as of 2016. For this rating section three different types of data from HealthGrades, 9 or 10 are the two highest possible ratings. Percentage of patients rating this hospital as a 9 or 10 - 67%.^[10]