Franklin Square is one of the five original open-space parks planned by William Penn when he laid out the city of Philadelphia, Pennsylvania, in 1682. It is located in the Center City area, between North 6th and 7th Streets, and between Race Street and the Vine Street Expressway (I-676).

Penn included this piece of green space in his original city plan as one of five squares, although the park was slow to develop because it was a marshy land. Originally, the park was a place for settlers to meditate and set a virtuous behavior to set a proper example. The park was supposed to be landscaped to have settlers understand the value of nature. In the 1920s, the park was abandoned and the surrounding area became known locally as the tenderloin with an entertainment district featuring taverns and bordellos, and became a place for individuals experiencing homelessness to sleep on the park's benches, resulting in its reputation as Philadelphia's skid row. In 2003, Historic Philadelphia, Inc. renovated the park by adding commercials and houses to attract tourists, which in turn helped the park back to its originality. Tourists are now able to enjoy the renovated park, family-friendly attractions, and the surrounding nature. Franklin Square is restored to its original plan as William Penn wanted the park to be used.

It is now managed by Historic Philadelphia, a non-profit organization.

Franklin Square was added to the National Register of Historic Places (NRHP) in 1981.