"Despacito" (Latin American Spanish: [despaˈsito]; transl. "Slowly") is a song by Puerto Rican singer Luis Fonsi, originally written in 2015. In 2016, Luis sent the song to Puerto Rican rapper and singer Daddy Yankee to give it an "urban injection", and released it as the lead single from Fonsi's 2019 studio album Vida.

Released on January 13, 2017, the song was written by Fonsi, Erika Ender, and Daddy Yankee, and produced by Mauricio Rengifo and Andrés Torres. A remix version featuring Canadian singer Justin Bieber was released on April 17, 2017, which helped to improve the chart performance of the song in numerous countries, including various number-one positions. "Despacito" has been widely credited by music journalists as being instrumental in the renewed popularity of Spanish-language pop music in the mainstream market.

It is a reggaeton and Latin pop song composed in common time with lyrics about desiring a sexual relationship, performed in a smooth and romantic way. "Despacito" received generally favorable reviews from music critics, who praised the fusion between Latin and urban rhythms, its catchiness, and its text painting. It has received Latin Grammy Awards for Record of the Year, Song of the Year, Best Urban Fusion/Performance, and Best Short Form Music Video at the 18th Latin Grammy Awards. "Despacito" has been also ranked among the best Latin songs of all time and the best songs of 2017 by various publications, which referred to it as one of the most successful Spanish-language tracks in pop-music history.

The song topped the charts of 47 countries and reached the top 10 of six others. In the United States, it became the first song primarily in Spanish to top the Billboard Hot 100 since Los del Río's "Macarena" in 1996, subsequently tying the longest-reigning number one on the Billboard Hot 100 at the time with 16 weeks, as well as becoming the longest-running number-one on the Hot Latin Songs chart with 56 weeks. It also became the first Latin song to receive a diamond certification by the Recording Industry Association of America. The music video shows both artists performing the song in La Perla neighborhood of Old San Juan, Puerto Rico and local bar La Factoría. It was the most-viewed YouTube video of all time from August 2017 to November 2020 when it was overtaken by Pinkfong's Baby Shark, and became the first video on the site to reach the milestones of three, four, five, six, seven, and eight billion views.

The lyrics of "Despacito" were written in late 2015 in Luis Fonsi's house in Miami because he wanted to record a "swinging song" for his new album after two years without releasing new music. He woke up mulling about "a song called 'Despacito'" and invited Brazilian-Panamanian singer and songwriter Erika Ender to a songwriting session. Fonsi co-wrote the song on a Gibson Emmylou Harris guitar. He originally composed it as a cumbia and pop song with lyrics written as a ballad, but decided to give it an "urban injection" and sent a demo to reggaeton artist Daddy Yankee. They recorded the song at Noisematch Studios in Miami in late 2016. Daddy Yankee improvised his verse in a corner of the studio's control room while thinking about his father playing bongos and wrote the post-chorus. It was produced by Mauricio Rengifo and Andrés Torres; the former is known as a member of Colombian pop duo Cali y El Dandee and the latter is known for previously working with David Bisbal, Thalía, and Ricky Martin. It was mixed by American engineer Jaycen Joshua at Larrabee Sound Studios in North Hollywood, Los Angeles.

Luis Fonsi does not consider it a reggaeton song, but feels, "it does have a reggaeton energy and an subtle urban beat". Ender stated that the track "went through several arrangements" until Fonsi got "exactly the arrangement he wanted". Fonsi described "Despacito" as a very melodic song that can adapt well to many other music genres. Due to the sensual nature of the song, they "needed to be responsible with a good lyric" and Ender's approach to writing for Fonsi was "to take care of how to say things with a good taste". In April 2017, American singer and songwriter Nicky Jam revealed that the original version of "Despacito" featured him instead of Daddy Yankee, but had to decline due to the song's release interfering with the launch of his album Fénix.

Three months after the release of "Despacito", Canadian singer Justin Bieber wanted to record a remix version after hearing the song in a Colombian nightclub during a tour in South America. The following day, Fonsi received a phone call from Universal Latin about the intentions for remix and authorized the label to send the track to Bieber. Bieber's manager, Scooter Braun, contacted his vocal producer Josh Gudwin to work on the song, who flew to Bogotá and recorded Justin Bieber's vocals at Estudios Audiovisión.

Bieber sang in Spanish for the first time in his career with the help of Colombian musician Juan Felipe Samper. What was most difficult for Justin Bieber was the 'ere' (ɾ) sound in words like "laberinto" (labyrinth), "paredes" (walls) and "manuscrito" (manuscript). Samper wrote the Spanish-language lyrics phonetically to ease Bieber's pronunciation, which was "perfectly" achieved in two hours. After a four-hour recording session, Gudwin sent Bieber's vocal tracks to Australian sound engineer Chris O'Ryan for vocal tuning. Gudwin concluded the remix's production in Parrot Cay, Turks and Caicos Islands with the mixing of Luis Fonsi's English-language vocals, whose lyrics were written by American songwriter Marty James. The entire process until the release date took six days. In June 2017, English musician Ed Sheeran revealed that he wanted to record a remix version of the song, but lost out to Justin Bieber.