| U.S. Open Cup | |
| Year: | 1991 |
| Country: | United States |
| Winners: | Brooklyn Italians |
| Second: | Richardson Rockets |
| Continental Cup Title: | 1992 CONCACAF Champions' Cup |
| Continental Cup Qualifiers: | Richardson Rockets |
| Continental Cup Title1: | 1991 CONCACAF Cup Winners Cup |
| Continental Cup Qualifiers1: | Brooklyn Italians |
| Prev Season: | 1990 |
| Next Season: | 1992 |
The 1991 United States Open Cup was the 78th edition of the soccer tournament to crown the national champion of the United States.
The Brooklyn Italians (NESSL) won the cup 1–0 against the Richardson Rockets (USISL) of Texas in a match played at Brooklyn College in Brooklyn, New York.