"Beso" (transl. "Kiss") is a song by Spanish singer Rosalía and Puerto Rican singer Rauw Alejandro for their collaborative extended play, RR (2023). The song's production was handled by Dylan Patrice, Alejandro, Rosalía, and Noah Goldstein. It was released by Columbia Records in partnertship with Sony Music Latin on March 24, 2023, as the lead single from the EP. A Spanish-language emo reggaeton and pop track, with an upbeat keyboard melody, it is a love song, in which they sing about longing for a kiss with each other, as well as their fear of separation.

"Beso" received positive reviews from music critics, who assumed that it would be one of the songs of the summer. The song was commercially successful, reaching number one in Spain, as well as the top five in several other countries such as Chile and Switzerland, and on Billboard's Hot Latin Songs in the United States. It also reached the summit of Latin Digital Song Sales and peaked at number 10 on Billboard Global 200. The song has received several certifications, including 8× platinum in Spain and diamond in France. An accompanying music video, released simultaneously with the song, was mainly made up of videos recorded by the singers in selfie mode and features a series of key moments the two had spent together during their relationship. They confirmed their engagement at the end of the video.

After months of exchanging Instagram direct messages, Rosalía and Rauw Alejandro met in person in Las Vegas during the 20th Annual Latin Grammy Awards in November 2019 and fell in love with each other. They began dating privately and worked together on several musical projects; Rosalía was featured as a background vocalist on Alejandro's "Dile a Él" (2020) and "Corazón Despeinado" (2022), and co-wrote "Caprichoso" (2022), while Alejandro co-wrote Rosalía's "Chicken Teriyaki" (2022). They made their relationship public in September 2021. During an interview with Billboard in May 2022, Alejandro spoke about collaborating with Rosalía:

For sure, we have a few [things planned] in the studio already. It's a surprise. Those songs are [under] extra security. We're planning to do the release — I'm not going to say when, but soon. We're doing it for the love of the fans and she's my girl and I did those songs with more love.

On March 13, 2023, the couple announced that they would release a three-song collaborative extended play titled RR on March 24, and revealed the tracks' titles as "Beso", "Vampiros", and "Promesa". On March 15, 2023, Rosalía shared a preview of "Beso" on TikTok, in which she was seen "on the verge of sharing a kiss" with Alejandro, while they were singing the song to each other. RR was released for digital download and streaming by Columbia Records on March 24, 2023, and "Beso" was included as the first track. On the same day, the song was picked as the lead single promoting the project, issued by Sony Music to Italian and Latin American radio stations.

Musically, "Beso" is a Spanish language emo reggaeton and pop song, with an upbeat keyboard melody. The New York Times reviewer Jon Pareles noted the singers' "high, small and tremulous" vocals over "a brusque beat topped with quasi-Baroque keyboards and strings". The track was written by Alejandro and Rosalía, while the production was handled by Dylan Patrice, Alejandro, Rosalía, and Noah Goldstein. It runs for a total of 3 minutes and 14 seconds. Lyrically, "Beso" which translates to "Kiss" in English, is a love song, in which they sing about longing for a kiss with each other, as well as their fear of separation. The lyrics include, "Ya yo necesito otro beso / Uno de esos que tú me da' / Estar lejos de ti e' el infierno / Estar cerca de ti es mi paz" (I need another kiss / One of those that you give to me / Being away from you is hell / Being close to you is my peace).

Upon release, "Beso" was met with widely positive reviews from music critics. Writing for Cosmopolitan, Natalia Arroyo assumed that it "is going to be one of the songs of the summer". Similarly, Happy FM staff labeled the track "a song that sounds like a hit" and believed that it "will be played a lot in the coming months", noting that "it has all the ingredients to be a new hit for the couple artists of the moment".

"Beso" became a global hit, bounding in Billboard Global 200 at number 10, with 50 million streams and 3,000 digital downloads sold worldwide in its first week. The song also debuted at number seven on Billboard Global Excl. US, earning Alejandro his fifth top 10 on the chart and Rosalía her fourth. The song debuted and peaked at number four on the US Billboard Hot Latin Songs chart on April 8, 2023, with a first-week tally of 2,000 downloads sold, 9.1 million streams, and 3 million radio impressions. Thus, it became Rosalía's seventh top 10 hit on the chart and Alejandro's tenth. It also reached number one on the US Latin Digital Song Sales, number ten on Latin Airplay, number three on Latin Rhythm Airplay, and number two on Latin Pop Airplay charts. On the US Billboard Hot 100, "Beso" debuted and peaked at number 52, giving both Rosalía and Alejandro their seventh entry. It also became the former's highest-charting song in her career, surpassing "La Noche de Anoche". In Canada, "Beso" debuted at number 85 on Billboard's Canadian Hot 100 on the chart issue dated April 8, 2023, earning Rosalía her fifth entry, and Alejandro his third. The song reached its peak of number 75 in the country on April 29, 2023.