Bryn Mawr is a census-designated place, located across 3 townships: Radnor Township and Haverford Township, Delaware County, and Lower Merion Township, Montgomery County, Pennsylvania, just west of Philadelphia along Lancaster Avenue.
There are also areas not in the census-designated place but which have "Bryn Mawr, Pennsylvania" postal addresses located in Radnor and Haverford Townships in Delaware County.
Bryn Mawr is located toward the center of what is known as the Main Line, a group of affluent Philadelphia suburban villages stretching from the city limits to Malvern. They became home to sprawling country estates belonging to Philadelphia's wealthiest families, and over the decades became a bastion of "old money". As of the 2010 census, it had a population of 3,779. Bryn Mawr is home to Bryn Mawr College.