Bryn Mawr is a census-designated place, located entirely in Lower Merion Township, Montgomery County, Pennsylvania, just west of Philadelphia along Lancaster Avenue and the border with Delaware County.
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. As of the 2010 census, it had a population of 3,779. Bryn Mawr is home to Bryn Mawr College.