| Ralph Onis | |
| Position: | Catcher |
| Bats: | Right |
| Throws: | Right |
| Birth Date: | 24 October 1908 |
| Birth Place: | Tampa, Florida, U.S. |
| Death Place: | Tampa, Florida, U.S. |
| Debutleague: | MLB |
| Debutdate: | April 27 |
| Debutyear: | 1935 |
| Debutteam: | Brooklyn Dodgers |
| Finalleague: | MLB |
| Finaldate: | April 27 |
| Finalyear: | 1935 |
| Finalteam: | Brooklyn Dodgers |
| Statleague: | MLB |
| Stat1label: | Batting average |
| Stat1value: | 1.000 |
| Stat2label: | Home runs |
| Stat2value: | 0 |
| Stat3label: | Runs batted in |
| Stat3value: | 0 |
| Teams: | |
Manuel Dominguez "Ralph" Onis (October 24, 1908 – January 4, 1995), nicknamed "Curly", was an American professional baseball player who played catcher in one game for the Brooklyn Dodgers on April 27, 1935. Onis singled in his only at-bat for a rare career batting average of 1.000.
His parents were born in Asturias, Spain, and he is buried in the Centro Asturiano de Tampa.
Onis managed in the Florida State League in 1939 and 1940.