New York State Route 100 (NY 100) is a major north–south state highway in Westchester County, New York, in the United States. It begins parallel to Interstate 87 (I-87) at a junction with the Cross County Parkway in the city of Yonkers and runs through most of the length of the county up to U.S. Route 202 (US 202) in the town of Somers. NY 100 was designated as part of the 1930 renumbering of state highways in New York. Prior to becoming a state road, various sections of NY 100 were part of several important early roads in the county.

Interstate 87 (I-87) is a 333.49-mile-long (536.70 km) north–south Interstate Highway located entirely within the US state of New York. I-87 is the main highway that connects New York City and Montreal. The highway begins at exit 47 off I-278 in the New York City borough of the Bronx, just north of the Robert F. Kennedy Bridge and Grand Central Parkway. From there, the route runs northward through the Hudson Valley, the Capital District, and the easternmost part of the North Country to the Canada–United States border in the town of Champlain. At its north end, I-87 continues into Quebec as Autoroute 15 (A-15). I-87 connects with several regionally important roads: I-95 in New York City, New York State Route 17 near Harriman, I-84 near Newburgh, and I-90 in Albany. The highway is not contiguous with I-87 in North Carolina.