The Diamond Rock Schoolhouse is a historic octagonal one-room school located in Tredyffrin Township, Chester County, Pennsylvania.

A local newspapers in 1940 described the schoolhouse as "one of the few remaining octagonal school buildings in Pennsylvania.

"[1] Constructed in 1818 at a cost of $260.93 by predominantly Mennonite families of Welsh and German descent, the schoolhouse was designed as an octagon because the shape provided one wall and window for each of the six grades and another for the teacher facing the door, with a wood-burning stove in the center of the room.

It fell into extreme disrepair until former pupils led by Emma Wersler (a member of the family that owned the property) banded together to restore and reopen the building in 1918.

It served as Wharton Esherick's painting studio for four years during the 1920s and hosted meetings of the local 4H Club and other groups during the 1940s.