English: St. Casimir Church, located at 8223 Sowinski Avenue in Cleveland, Ohio, in the United States.

St. Casimir Parish was erected in 1892. In 1894, a two-story brick structure was built on the southeast corner of Pulaski Avenue and E. 82nd Street. The church occupied the first floor, and a parochial school the second. Between 1903 and 1911, a rectory was built opposite the church on E. 82nd Street (where the convent now stands).

Construction of a new, $150,000 church structure began in June 1918. It was designed by local architect William Jansen in the "Polish Cathedral style", a mixture of Romanesque Revival and vernacular architecture unique to the Midwest region. The first floor of the old building was converted for use by the school.

Between 1924 and 1934, a new rectory was built, a new convent erected on the site of the old rectory, stained glass windows for the church purchased, bells for the church obtained, and the rest of the block purchased for expansion.

The original church was demolished in 1948 and a new school completed in 1949. A new convent was built in 1955, and a new parish hall in 1962.

The school closed in 1976, and the convent about 1982. (It is not clear if the convent is in use as of 2017.) In 2009, the Diocese of Cleveland attempted to close St. Casimir Church as part of a diocese-wide closure of more than 50 parishes. Members of the parish appealed to the Vatican, which overturned the closure. St. Casimir Church reopened in 2010.

In 2017, St. Casimir Church began an extensive construction project to build rainwater catchments beneath most of its property as part of an effort to transform its campus into a "green" facility.