Robert Treat Paine (October 28, 1835 – August 11, 1910) was an American Boston-based lawyer, philanthropist, and social reformer.

He is most widely known for his work as chairman of the building committee of Boston's Trinity Church in Copley Square, for his leadership of 19th century Boston philanthropists, for his summer home in Waltham, Massachusetts, and for his experiments in building housing for low- and middle-income workers.

For many years, Paine was counsel for Calumet and Hecla Mining Company as well as for the Chicago, Burlington and Quincy Railroad as it expanded westward.

[2][3] Paine, having invested in real estate, mining, and railroad enterprises, retired in 1870 and devoted his time to humanitarian work.

Another of his housing experiments, an 1890s 100-house subdivision between Round Hill and Sunnyside streets in Jamaica Plain, has been deemed eligible for nomination to the National Register.