Mallex Lydell Smith (born May 6, 1993) is an American professional baseball outfielder for the Pericos de Puebla of the Mexican League.

He has previously played in Major League Baseball (MLB) for the Atlanta Braves, Tampa Bay Rays, and Seattle Mariners.

Smith had a breakout season in 2018, making the Opening Day roster and hitting .296/.367/.406 in a career-high 141 games with a 3.5 bWAR.

[12] He finished the year hitting .310 with five home runs and led all minor league players in stolen bases with 88.

Smith's helmet lacerated his forehead on a stolen base attempt in the fourth inning, and he left the game.

[29] Smith spent the 2016 offseason with the Naranjeros de Hermosillo of the Liga Mexicana del Pacífico and was released in October.

[32] On January 11, 2017, the Braves traded Smith, along with Shae Simmons, to the Seattle Mariners in exchange for minor-league pitchers Luiz Gohara and Thomas Burrows.

[33] That same day, the Mariners traded Smith, Ryan Yarbrough, and Carlos Vargas to the Tampa Bay Rays for Drew Smyly.

[35] A longtime fan of Friday the 13th, Smith said after his trade to the Rays that the franchise's main character Jason Voorhees represents his effort to be opposing teams' "worst nightmare.

"[35] On April 9, after reaching base five times (a single, double and three walks), stealing two bases, and scoring the walk-off run in a 3-2 victory against the Toronto Blue Jays, Chris Archer coined the term "Mallex Effect" to describe Smith's ability to wreak havoc and change games with his scrappy and speedy play.

[37] On August 18, Smith was optioned down to Triple-A Durham to make room for Kevin Kiermaier, who was returning off the disabled list.

[39] Smith made the opening day roster in 2018 with the plan to platoon with Denard Span in left field.

[41] Smith was announced as a nominee for the Roberto Clemente Award, which is the recognition of a player who best represents the game of baseball through extraordinary character, community involvement, philanthropy and positive contributions on and off the field.

[43] Smith ended his breakout season setting career highs, he slashed .296/.367/.406 in 544 plate appearances over 141 games (which led the team), recording 40 stolen bases (second in the American League), 10 triples (tied for most in the American League), 65 runs, and 40 runs batted in.

On November 8, 2018, the Rays traded Smith back to the Mariners along with minor-leaguer Jake Fraley in exchange for Mike Zunino, Guillermo Heredia, and Michael Plassmeyer.

[45][46] During Spring Training, Smith injured the flexor bundle in his right arm when overdoing his throwing routine, sidelining him for the 2019 Opening Series in Tokyo, Japan.

[56] On November 29, Smith signed a minor league contract with the Blue Jays and was invited to spring training.

On June 12, 2022, Smith signed with the Kansas City Monarchs of the American Association of Professional Baseball.