"Mr. Simple" is a song by South Korean boy band Super Junior, released as their tenth Korean and lead single off their fifth studio album of the same name digitally on August 2, 2011, via SM Entertainment in South Korea. The song topped the charts hours after its release.

The Japanese version of the song was released as their second Japanese single on December 7, 2011, under Avex Trax. A b-side track of the single entitled "Snow White" was revealed via the group's official Japanese website on November 30, 2011. The single debuted at #2 in the Oricon Weekly Charts, selling 89,000 copies on its first week of release, outselling their previous Japanese single Bijin (Bonamana) which sold 59,000 on its first week and 67,000 on total sales, making it Super Junior's highest-selling Japanese release yet. The song was used as a commercial tie-up for Japanese satellite communication holding company SKY Perfect JSAT Group. It will also became an ending theme song of TBS's Tsubo Musume for January 2012.

Mr. Simple became the 85th best-selling single of 2011 in Japan according to the Oricon charts and is certified Gold by the RIAJ for 100,000 units shipped to Japanese music stores.

The song was released along with the rest of the album's tracks on August 2, 2011, and has topped online charts hours after its release. The song was written by Yoo Young-jin, which was also the writer of their previous lead singles "Twins (Knock Out)", "Don't Don", "Sorry, Sorry" and "Bonamana". SM Entertainment describes the song as:

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