The Robert Treat Paine Estate, known as Stonehurst, is a country house set on 109 acres (44 ha) in Waltham, Massachusetts.

In 1866, Boston lawyer Robert Treat Paine Jr. and his wife Lydia (Lyman) commissioned architect Gridley James Fox Bryant to build a mansarded Second Empire summer house in Waltham.

In October 1883, Richardson and Olmsted made their first visit to the property to discuss relocating the house and expanding it.

In July 1884, Olmsted and Richardson produced sketches for a new site atop a rocky ridge with sweeping views to the southeast.

In 1974 Theodore Lyman Storer donated the 113-acre (46 ha) property to the city of Waltham.