Mount Airy is bounded on the northwest by the Cresheim Valley, which is part of Fairmount Park.
Beyond this lies Chestnut Hill.
On the west side is the Wissahickon Gorge, which is also part of Fairmount Park, beyond which lies Roxborough and Manayunk.
Germantown borders the southeast of Mount Airy, and Stenton Avenue marks the northeast border.
Beyond Stenton Avenue is Cedarbrook and West Oak Lane.

The USPS does not officially correlate neighborhood names to Philadelphia ZIP codes (all are called simply "Philadelphia" or "Phila").
However, the 19119 ZIP code is almost entirely coterminous with the cultural-consensus boundaries of Mount Airy.

There is no official boundary between Mount Airy and Germantown.
The most common consensus is that Johnson Street is the de facto boundary; however, the West Mount Airy Neighbors and East Mount Airy Neighbors organizations consider Washington Lane to be Mount Airy's southern edge.
The question is moot, however, as the two neighborhoods blend together very gradually.
Historically, the entire area was part of the German Township.
Many buildings in Mount Airy carry the identity and even the name of Germantown in one way or another.
For example, the Unitarian Society of Germantown, the Germantown Jewish Centre, the Germantown Christian Assembly, and the Germantown Montessori School are all in Mount Airy, yet also belong culturally to Germantown.
Parts of the Battle of Germantown in 1777 occurred throughout Mount Airy.
The special relationship linking the two has its roots in the time before the Act of Consolidation, when Germantown was a borough separate from the City of Philadelphia, and its rural environs were what is now Mount Airy.
Mount Airy is bounded on the northwest by the Cresheim Valley, which is part of Fairmount Park. Beyond this lies Chestnut Hill. On the west side is the Wissahickon Gorge, which is also part of Fairmount Park, beyond which lies Roxborough and Manayunk. Germantown borders the southeast of Mount Airy, and Stenton Avenue marks the northeast border. Beyond Stenton Avenue is Cedarbrook and West Oak Lane.
The USPS does not officially correlate neighborhood names to Philadelphia ZIP codes (all are called simply "Philadelphia" or "Phila"). However, the 19119 ZIP code is almost entirely coterminous with the cultural-consensus boundaries of Mount Airy.
There is no official boundary between Mount Airy and Germantown. The most common consensus is that Johnson Street is the de facto boundary; however, the West Mount Airy Neighbors and East Mount Airy Neighbors organizations consider Washington Lane to be Mount Airy's southern edge. The question is moot, however, as the two neighborhoods blend together very gradually. Historically, the entire area was part of the German Township. Many buildings in Mount Airy carry the identity and even the name of Germantown in one way or another. For example, the Unitarian Society of Germantown, the Germantown Jewish Centre, the Germantown Christian Assembly, and the Germantown Montessori School are all in Mount Airy, yet also belong culturally to Germantown. Parts of the Battle of Germantown in 1777 occurred throughout Mount Airy. The special relationship linking the two has its roots in the time before the Act of Consolidation, when Germantown was a borough separate from the City of Philadelphia, and its rural environs were what is now Mount Airy.
Mount Airy, Philadelphia