Clara Maass Medical Center is a 342- bed hospital in Belleville, Essex County, New Jersey, United States, that is part of the RWJBarnabas Health system.

[1] It was founded in 1868 as the Newark German Hospital, and was renamed in 1952 in honor of Clara Maass, a former nurse who trained there at the hospital's Christina Trefz Training School for Nurses, and become the hospital's head nurse.

Maass' 1901 death during yellow fever experiments attracted national attention.

[2] In 1956 a new building was completed in Belleville, which is sometimes referred to as "The Hospital in the Park" due to its location opposite Branch Brook Park.

[3] In 2022, the hospital was staffed by over 700 physicians with 2,100 total employees.