Bryn Mawr is located towards the center of the Main Line. The name Bryn Mawr means "big hill" in Welsh and takes its name from an estate near Dolgellau in North Wales.

According to the United States Census Bureau, the CDP has a total area of 0.6 square miles (1.6 km?), all land and entirely within Lower Merion Township in Montgomery County.[5] However, the "Bryn Mawr" zip code (19010) covers a larger area, and as a result, the geographic term "Bryn Mawr" is often used in a sense that includes not only the CDP, but also other areas that share the zip code. These other areas include the community of Rosemont within Lower Merion Township and Radnor Township, and various other areas within Lower Merion Township, Radnor Township, and Haverford Township. As of the 2000 Census, the Bryn Mawr ZIP code was home to 21,485 people with a median family income of $110,956.

Bryn Mawr residents of Lower Merion Township attend schools in the Lower Merion School District; all residents of the Bryn Mawr CDP are in Lower Merion Township and therefore attend LMSD schools.

Bryn Mawr address residents of Radnor Township attend schools in the Radnor Township School District; Radnor High School is the district's sole high school.

Bryn Mawr address residents of Haverford Township attend schools in the School District of Haverford Township; Haverford High School is the district's sole high school.