Tibbetts Brook, originally Tippett's Brook or Tibbitt's Brook, is a stream in the southern portion of mainland New York, flowing north to south from the city of Yonkers in Westchester County into the borough of the Bronx within New York City. Originally emptying into Spuyten Duyvil Creek as part of the Harlem River system, the stream is now partially subterranean, ending above ground at the south end of Van Cortlandt Lake within Van Cortlandt Park. There it proceeds into city sewers, draining into either the northern end of the Harlem River or the Wards Island Water Pollution Control Plant. The brook provides significant watershed to both Van Cortlandt Park at its south end and Tibbetts Brook Park at its north end. There have been modern proposals to daylight the southern portion of the brook back onto the surface.

Westchester County is located in the U.S. state of New York. It is the seventh most populous county in the State of New York and the most populous north of New York City. According to the 2020 United States Census, the county had a population of 1,004,456, its highest decennial count ever and an increase of 55,344 (5.8%) from the 949,113 counted in 2010. Westchester covers an area of 450 square miles (1,200 km2), consisting of six cities, 19 towns, and 23 villages. Established in 1683, Westchester was named after the city of Chester, England. The county seat is the city of White Plains, while the most populous municipality in the county is the city of Yonkers, with 211,569 residents per the 2020 census. The county is part of the Hudson Valley region of the state.