Eli Porter Ashmun (June 24, 1770-May 10, 1819) was a Federalist United States Senator from Massachusetts from 1816 to 1818.
Born in a small village north of Albany, New York on the Hudson River, he attended the local school and attended Middlebury College, graduating in 1807. He was a Member of the Massachusetts House of Representatives from 1803-04. He studied law, was admitted to the state bar and began his practice in Blandford, soon moving to Northampton, and was in the Massachusetts Senate from 1808-10. In 1816, he served with the Massachusetts Governor's Council. Following the resignation of Senator Christopher Gore, he was elected to the US Senate, serving from June 12, 1816, to May 10, 1818. He died in 1819 and is interned in Bridge Street Cemetery in Northampton.
Ashmun had one wife, Lucy, who died in 1812 at the age of 37. He was the father of George Ashmun (1804-1870), who served in the U.S. House of Representatives.