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The 1991 U.S. Women's Hardcourt Championships was a women's tennis tournament played on outdoor hard courts at the McFarlin Tennis Center in San Antonio, Texas in the United States and was part of the Tier III category of the 1991 WTA Tour. It was the 26th edition of the tournament and was held from March 25 through March 31, 1991. Second-seeded Steffi Graf, who entered the main draw on a wildcard, won the singles title, her third at the event after 1988 and 1989, and earned $45,000 first-prize money.
Steffi Graf
Patty Fendick / 
Elizabeth Smylie
Monica Seles 6–4, 6–3
Jill Hetherington /