St. Paul's Protestant Episcopal Church, more commonly called Old St. Paul's Church today, is a historic Episcopal church located at 233 North Charles Street at the southeast corner with East Saratoga Street, in Baltimore, Maryland, near "Cathedral Hill" on the northern edge of the downtown central business district to the south and the Mount Vernon-Belevedere cultural/historic neighborhood to the north. It was founded in 1692 as the parish church for the "Patapsco Parish", one of the "original 30 parishes" of the old Church of England in colonial Maryland.

Charles Street, known for most of its route as Maryland Route 139, runs through Baltimore and the Towson area of Baltimore County. On the north end, it terminates at an intersection with Bellona Avenue near Interstate 695 (I-695). At the south end, it terminates in Federal Hill in Baltimore. Charles Street is one of the major routes through Baltimore, and is a major public transportation corridor. For the one-way portions of Charles Street, the street is functionally complemented by the parallel St. Paul Street, including St. Paul Place and Preston Gardens, Maryland Avenue, Cathedral Street, and Liberty Street.