"Let's Get Loud" is a song recorded by American singer Jennifer Lopez for her debut studio album On the 6 (1999). Originally written by the song's co-writer Gloria Estefan for herself, she felt as if the song was too similar to her previous material and passed it onto Lopez. Estefan, who co-wrote the song alongside Kike Santander, stated that she would have "more fun with it" and would put "a new spin" on it. "Let's Get Loud" is often regarded as Lopez's signature song. Estefan eventually released her own version of the song in 2011 as a bonus track on the deluxe Target edition of her album Miss Little Havana.
After a series of co-starring film roles, Lopez received her big break in 1996, when she was cast to play the title role in Selena, a biopic of the late American singer-songwriter Selena. In the film, Selena's real voice is used for the musical sequences, but Lopez would nonetheless sing the lyrics during the scenes instead of lip syncing. When asked by an interview if Selena inspired her to launch a music career, Lopez stated: "I really, really became inspired, because I started my career in musical theater on stage. So doing the movie just reminded me of how much I missed singing, dancing, and the like..." After filming Selena, Lopez was "really feeling [her] Latin roots" and cut a demo in Spanish. Lopez's manager then sent the song, entitled "Vivir Sin Ti", to Sony Music Entertainment's Work Records, who showed an interest in signing Lopez. Tommy Mottola, the head of the label suggested to her that she sing in English instead. She complied and began recording her debut studio album On the 6. During production of the On the 6, Lopez was aware of the fact that she received her recording contract on the premise of her looks and having an already established name in the entertainment industry, and wanted to prove that she had musical talent. Prior to the debut of her music, critics wondered why she would take the risk of launching a music career. It was noted that: "If the album was a flop, not only would it embarrass Lopez, but it might even damage her career."
"Let's Get Loud" was originally written for Gloria Estefan, but she felt as if the song was too similar to her previous recordings. She then passed the song to Lopez, stating that she would have "more fun with it" and would put "a new spin" on it. "Let's Get Loud" was written by Estefan and Kike Santander, who also arranged and co-produced the song alongside Emilio Estefan Jr.. Javier Garza and Marcelo Anez recorded Lopez's vocals for the song at Crescent Moon Studios in Miami, Florida. Pablo Flores mixed the song at Crescent Moon Studios in Miami, Florida.
Mario Tarradell from The Dallas Morning News complimented the Latin flavor in the song, writing "Jennifer Lopez wastes no time asserting her Latina heritage: "Let's Get Loud," a cut from the actress—turned—singer's debut album, On the 6, opens with a sassy declaration – '¡Ya Jenny llego, presente!'" Heather Phares from AllMusic, on her review of On the 6 gave a positive review of the song, stating that "'Let's Get Loud' have a fiery, soulful sound more in keeping with Lopez's public persona." Michael Paoletta from Billboard, commented that the song's remixes "deliver the goods in a variety of ways", further explaining that the Kung Pow "ups the ante" with the Castle Hills Club mix, considering that it "overflows with diva attitude and Latin/pop sensibilities." Richard Torres from Newsday gave a negative review of the song, stating that it was a "total misfire" and that "Lopez simply doesn't supply enough oomph to drive this salsa-injected tune. She's far too feathery where she should truly get down." At the 43rd Grammy Awards in 2001, Lopez earned her second consecutive nomination for the Grammy Award for Best Dance Recording (having been nominated for "Waiting For Tonight" in 2000).
"Let's Get Loud" debuted on the Australian Singles chart at number 49 the week ending August 20, 2000. On the week ending November 12, 2000, the song reached its peak at number nine and stayed there for five consecutive weeks. In Austria, the song debuted at number 35 on the week ending July 9, 2000 and reached its peak of eleven August 20, 2000. "Let's Get Loud" fared better on Italy and Netherlands. On the former, it debuted at number twelve the week ending June 22, 2000 and reached its peak at number six the following week, managing to stay inside the top ten for five consecutive weeks before dropping of the chart. On the latter, it reached number three, becoming the highest peak of the song in all music markets. In the United States, the song became, after "No Me Ames", the second single from On the 6 that failed to chart inside the US Billboard Hot 100. The song, however, appeared at number 39 on the US BillboardHot Dance Club Play chart. "Let's Get Loud" later appeared at number 25 on the Australian year-end charts of 2000. It has sold 413,000 digital downloads in the United States as of 2013.
Lopez performed "Let's Get Loud" as part of her 2012 Dance Again World Tour. She emerged on-stage wearing a tuxedo with pink ruffles while playing a bongo, before transitioning into "Let's Get Loud". During the performance, her dancers ripped off the tuxedo to reveal a black-laced body suit. The song was included on the set list for her Las Vegas residency, All I Have, which commenced in January 2016. Lopez performed "Let's Get Loud" on the series finale of American Idol on April 7, 2016, alongside her single "Ain't Your Mama".