The 1991 U.S. Pro Indoor was a tennis tournament played on indoor carpet courts that was part of the Championship Series of the 1991 ATP Tour. It was played at the Wachovia Spectrum in Philadelphia, Pennsylvania in the United States from February 11 to February 18, 1991.

Ivan Lendl defeated Pete Sampras 5–7, 6–4, 6–4, 3–6, 6–3

Rick Leach / Jim Pugh defeated Udo Riglewski / Michael Stich 6–4, 6–4