The 1991 U.S. Women's Open Golf Championship was the 46th edition of the U.S. Women's Open, held July 11–14 at Colonial Country Club in Fort Worth, Texas. Meg Mallon shot a final round 67 (−4) to finish at 283 (−1), two strokes ahead of runner-up Pat Bradley. Mallon trailed Bradley by three strokes with ten holes to play. It was the second of Mallon's four major titles; she won the LPGA Championship two weeks earlier. Mallon won her second U.S. Women's Open and final major thirteen years later in 2004.
Play was so painstakingly slow during the first round that Lori Garbacz decided to protest. While playing the 14th hole, Garbacz had her caddie go to a nearby pay phone and order a pizza that she wanted delivered to the 17th tee. The pizza was waiting for Garbacz and she had plenty of time to eat it, as there were two groups ahead of her waiting to tee off.
Mallon won $110,000, the championship's first six-figure winner's share. It was an increase of nearly 30% over the previous year and double that of just four years earlier.
Through 2015, this is the only time the championship has been played in the state of Texas. Colonial has been an annual stop on the PGA Tour since 1946; now known as the Crowne Plaza Invitational at Colonial, it is usually played in May. It also hosted the U.S. Open in 1941, the last before World War II.