Amasa Mason Eaton (May 31, 1841 – October 3, 1914) was an American lawyer and politician. Born in Providence, Rhode Island, Eaton briefly served in the Union Army after graduating from Brown University. In the 1860s and 1870s, he held various political positions in Rhode Island, including a seat in the Rhode Island House of Representatives. After receiving a law degree from Harvard University, he published on topics including municipal government and free trade.