"Hello" is a song by English singer-songwriter Adele, released on 23 October 2015 by XL Recordings as the lead single from her third studio album, 25. Adele co-wrote the song with her producer, Greg Kurstin. "Hello" is a piano ballad with soul influences and lyrics that discuss themes of nostalgia and regret. Upon release, the song was acclaimed by music critics, who compared it favorably to Adele's previous works and praised its lyrics, production, and Adele's vocal performance. It was recorded in London's Metropolis Studios.

"Hello" topped the charts in a record-breaking 36 countries, including the United Kingdom, where it became Adele's second chart-topper, following "Someone Like You", and had the largest opening week sales in three years. In the United States, "Hello" debuted atop the Billboard Hot 100, reigning for ten consecutive weeks whilst becoming Adele's fourth number-one single on the chart and breaking several records, including becoming the first song to sell over a million digital copies in a week. By the end of 2015, it had sold 12.3 million units globally and was the year's 7th best-selling single while it stands as one of the best-selling digital singles of all-time.

The accompanying music video was directed by Xavier Dolan and co-stars Adele and Tristan Wilds. The music video for the song broke the Vevo Record by achieving over 27.7 million views within a 24-hour span, held previously by Taylor Swift's "Bad Blood" which accumulated 20.1 million views in that timeframe. "Hello" also broke the record for the shortest time to reach one billion YouTube views. The music video for the song received seven nominations at the 2016 MTV Video Music Awards, including Video of the Year and Best Female Video. At the 59th Annual Grammy Awards, "Hello" won three awards; Record of the Year, Song of the Year, and Best Pop Solo Performance. The song also won the Brit Award for Song of the Year and the APRA Award for International Work of the Year.