"Telephone" is a song by American singer Lady Gaga from her third extended play (EP), The Fame Monster (2009)—the reissue of her debut studio album, The Fame (2008). Featuring American singer Beyoncé, it was released as the EP's second single on January 26, 2010. Gaga and Rodney Jerkins wrote and produced "Telephone", with additional songwriting by LaShawn Daniels, Lazonate Franklin and Beyoncé. Gaga originally wrote the song for Britney Spears, who recorded a demo. "Telephone" conveys Gaga's fear of not finding time for fun given the increasing pressure for her to work harder as an artist. Musically, the song consists of an expanded bridge, verse-rap and a sampled voice of an operator announcing that the phone line is unreachable. Beyoncé appears in the middle of the song, singing the verses in a "rapid-fire" way, accompanied by double beats.

"Telephone" received positive reviews from critics who called it a stand-out track from The Fame Monster and praised Gaga's chemistry with Beyoncé. Several critics included it in their best-of list of 2010. It was nominated for a Grammy Award for Best Pop Collaboration with Vocals, and won a ASCAP Pop Music Award and a BMI Award. Following the album's release, the song charted in many countries, including Australia, Canada, the Netherlands, New Zealand, Sweden and Hungary. Peaking at number three in the US, it was particularly successful in Europe where it topped the charts in Belgium, Croatia, Denmark, Ireland, Norway and the UK. The song sold 7.4 million digital copies worldwide in 2010, making it the year's fourth best-selling single.

Shot as a short film, the accompanying music video is a continuation of the video for "Paparazzi" (2009), the fifth single from The Fame. It follows Beyoncé as she bails Gaga out of prison for killing her boyfriend; they go to a diner and poison the customers' breakfast. The video ends as they attempt to escape a high-speed police chase. It references Quentin Tarantino and his films Pulp Fiction (1994) and Kill Bill: Volume 1 (2003). The video received generally positive reviews and was nominated for three awards at the 2010 MTV Video Music Awards, including Video of the Year. In January 2015, Billboard named it the best video of the decade. NME listed it as one of the 100 greatest music videos of all time. Retrospective reviewers analyzed the video's themes, including feminism, lesbianism, and commentary on fame and celebrity culture.

In memory of fashion designer and friend Alexander McQueen, Gaga performed an acoustic rendition of "Telephone" at the 2010 BRIT Awards. She also sang it during the Super Bowl LI halftime show, and many of her concert tours and other live appearances. The song was covered by several artists, as well as characters from the television show Glee.