Marcellus is a town in Onondaga County, New York, United States.

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.

High hills, deep valleys, lake and streams, make the town remarkably scenic.

Nine Mile Creek is a noted trout stream where New York State provides several access areas.

Marcellus was a named township in the former Central New York Military Tract.

The Tefft-Steadman House was listed on the National Register of Historic Places in 2007.

22.3% of all households were made up of individuals, and 9.5% had someone living alone who was 65 years of age or older.