David Marshall Long (October 23, 1936 – December 19, 2018) was an American politician in the state of Kentucky.
He served in the United States Air Force and was commissioned a captain.
Marshall received his bachelor's degree from Centre College in 1959.
He lived in Shelbyville, Kentucky and was in the real estate business.
A 1998 survey by the Kentucky Center for Public Issues rated Long as the most effective legislator in the house.