Marcellus is a town in Onondaga County, New York, United States. The population was 6,210 at the 2010 census. The town was probably named after Marcus Claudius Marcellus, a Roman general, by a clerk interested in the Classics.
The Marcellus Formation is a vast geological layer of shale spanning Pennsylvania, West Virginia and parts of other states and Ontario, which is named for an outcropping in or near Marcellus.
The town was formed in 1794, The Town of Geddes was removed in 1798. The township of Camillus was taken off in 1799. Otisco was removed in 1806. In 1830, the west part of the town was used for the new Town of Skaneateles. Marcellus regained territory in 1840 from Spafford and Otisco.