The 1991 Westchester Cup was a women's tennis tournament played on outdoor hard courts at the Manhattanville College in Westchester, New York in the United States.

It was the 9th and final edition of the event played in the state of New York since 1968 where it originated as the Madison Square Garden Challenge Trophy, the second played in Westchester, and was part of the Tier V series of the 1991 WTA Tour.

Unseeded Isabelle Demongeot won the singles title and earned $18,000 first-prize money.

Isabelle Demongeot defeated Lori McNeil 6–4, 6–4 Rosalyn Fairbank / Lise Gregory defeated Katrina Adams / Lori McNeil 7–5, 6–4

This WTA Tour tennis tournament article is a stub.