Yacksel Ríos Melendez[a] (born June 27, 1993) is a Puerto Rican professional baseball pitcher in the New York Mets organization.

He has previously played in Major League Baseball (MLB) for the Philadelphia Phillies, Pittsburgh Pirates, Seattle Mariners, Boston Red Sox, and Oakland Athletics.

[3] He made his professional debut later that year, with the Gulf Coast League Phillies where he pitched to a 0–1 record, and 8.47 ERA, in 11+1⁄3 innings.

The next year, 2016, again found him with Clearwater, the GCL Phillies, and the Reading Fightin Phils, where he was a combined 5–4, with a 5.74 ERA, in 37 games (seven starts).

On January 21, 2021, Ríos signed a minor league contract with the Tampa Bay Rays organization and was invited to spring training.

[13] He made his Red Sox debut on June 16, retiring the one batter he faced and earning a win in relief against the Atlanta Braves.

[18] In 21 appearances for the Triple–A Gwinnett Stripers, Ríos logged a pristine 1.46 ERA with 30 strikeouts and 7 saves across 24+2⁄3 innings.

On March 13, 2023, he pitched in relief versus Israel and retired every batter faced over after José De León tossed 5+2⁄3 perfect innings.

Edwin Díaz, and Duane Underwood Jr. each relieved De León and retired every batter faced, and Martín Maldonado caught on the way to a 10–0 win.

The contest ended when Maldonado scored on a walk-off hit in the bottom of the eighth inning that invoked the tournament's mercy rule.

However, it did not qualify as an official perfect game per the Elias Sports Bureau, due to lasting fewer than nine innings.