Irondequoit Bay is a large body of water located in northeastern Monroe County, New York.

The Irondequoit–Penfield boundary continues along the center of Irondequoit Creek south of the New York State Route 404 float bridge.

The most recent glacier that left evidence here was about 100,000 years ago and it caused compression of the earth by as much as 2,500 feet (760 m).

[4] About 12,000 years ago, the area underwent massive changes, which included the rerouting of the Genesee River and other water bodies.

[5] On a French map of the area from 1688 titled "Le Lac Ontario"[6] Irondequoit Bay was referred to as the "swamp of the Senecas".