St. Vincent Archabbey Gristmill, also known as The Gristmill, is a historic grist mill located in Unity Township, Westmoreland County, Pennsylvania.

The original section was built in 1854, and is a four-story, frame structure measuring 45 by 40 feet (14 m × 12 m).

The mill operated by steam and remains in use.

It was built as part of Saint Vincent Archabbey, the first Benedictine Monastery in the United States, which opened in 1846.

[2] It was added to the National Register of Historic Places in 1978.