Jamesville is a hamlet in De Witt, Onondaga County, New York, United States, part of the greater Syracuse area. The history of the community is documented in the book Water, Wheels and Stone: Heritage of the Little Village by the Creek, Jamesville, New York, written by Jean Schutz Keough, and published in 1976 and 1978 by the Jamesville Historical Book Committee. Jamesville is the site of the Jamesville Reservoir. The reservoir is in a park that contains a small beach, several short hiking trails and fields. The fields are the site of the annual Jamesville BalloonFest where dozens of hot-air balloons take to the air in one weekend. Jamesville was formerly served by OnTrack, a commuter rail system that ceased operations in 2007.