Samuel Merrill III (born 1939) is a mathematician and political scientist best known for his work on alternative voting systems, voter behavior, party competition, and arbitration.

Merrill was raised in Bogalusa, Louisiana. He received his Bachelor's degree from Tulane University and his Ph.D. from Yale University in mathematics. Merrill was a professor of mathematics and statistics at Wilkes University until he retired in 2004.

Samuel Merrill is the author of three books on political science:

• Making Multicandidate Elections More Democratic (1988, Princeton University Press)
• A Unified Theory of Voting with Bernard Grofman (1999, Cambridge University Press)
• A Unified Theory of Party Competition with James Adams and Bernard Grofman (2005, Cambridge University Press)