Mario Melvin Soto (born July 12, 1956) is a Dominican former pitcher, mostly as a starter, for the Cincinnati Reds of Major League Baseball (MLB) from 1977 through 1988.

He possessed a hard fastball (clocked in the low-to-mid 90s) and complemented it with a baffling circle changeup, both thrown from the three-quarters position.

However, with two out in the top of the ninth inning and the Reds up 1–0, outfielder George Hendrick spoiled the no-hitter with a game-tying solo home run.

He compiled a 35–20 record with a 2.92 earned run average and he established himself as the ace of the Cincinnati Reds' rotation.

He allowed 1,395 hits, 667 earned runs, 657 bases on balls and struck out 1,449 batters in 1,7301⁄3 innings pitched.

On April 29, 1986, against the Montreal Expos, Soto became the 11th pitcher in major league history to surrender four home runs in an inning.

Four days later, National League president Chub Feeney suspended Mario Soto for five games.

[3] Soto is credited as the person who taught Edinson Vólquez and Johnny Cueto their change-ups, which have been go-to strikeout pitches in their careers.