"I'll Be Missing You" is a tribute song by American rapper Puff Daddy and American singer Faith Evans, featuring American R&B group 112. The song honors the Notorious B.I.G., a fellow artist on Puff Daddy's Bad Boy Records and Evans's husband, who was murdered on March 9, 1997. It was released in May 1997 by Bad Boy and Arista Records as the second single from Puff Daddy's debut studio album, No Way Out (1997).

The track incorporates a prominent sample from the Police's 1983 song "Every Breath You Take", with an adapted chorus performed by Evans. It also includes elements from the 1929 hymn "I'll Fly Away" by Albert E. Brumley and features a spoken introduction layered over a choral arrangement of Samuel Barber’s "Adagio for Strings". The song’s music video was directed by Hype Williams and filmed at various locations in Chicago.

At the 40th Annual Grammy Awards, "I'll Be Missing You" won the Grammy Award for Best Rap Performance by a Duo or Group. The single spent eleven consecutive weeks at number one on the US Billboard Hot 100 and reached the top position in 15 other countries. It was the best-performing single of 1997 in Iceland, the Netherlands (Dutch Top 40), and Romania. With shipments of over three million copies in the United States and more than one million copies in both Germany and the United Kingdom, the song is regarded as one of the best-selling singles of all time.

"I'll Be Missing You" is based on a slightly slowed down sample of the 1983 single "Every Breath You Take" by the Police. It also uses an interpolation of the "Every Breath You Take" melody, sung by Biggie's widow, Faith Evans. Combs did not secure legal approval for the sample before releasing the song, and Police songwriter Sting sued, receiving 100% of the song royalties (with some reports estimating $2,000 per day). Police guitarist Andy Summers called the sample "a major rip-off", and told the A.V. Club: "I found out about it after it was on the radio ... I’d be walking round Tower Records, and the fucking thing would be playing over and over. It was very bizarre while it lasted." Sting later reconciled with Bad Boy, and performed the song alongside Puff Daddy and Evans in September 1997 at the MTV Video Music Awards.

The track uses the melody from the 1929 hymn, "I'll Fly Away". Combs' verses were written by rapper Sauce Money. Combs had originally asked Jay-Z to write the track, but he turned it down and suggested that Sauce Money write the song instead.

Tom Sinclair from Entertainment Weekly panned the song, giving it a grade of D and describing it as a "maudlin 'tribute' to the Notorious B.I.G., [in which] the late rapper's former mentor (Puff Daddy) and wife (Faith Evans) team up to say their farewells to the big man on a song that 'samples' The Police's 'Every Breath You Take'. With lyrics like 'Know you're in heaven, smiling down/Watching us while we pray for you', 'I'll Be Missing You' gives the lie to those who claim hip-hoppers are above self-serving sentimentality." British magazine Music Week gave it four out of five and named it a "dignified tribute". Also James Hyman from Record Mirror gave the song four out of five, noting that "once again, blatant plundering from an Eighties groove forms the basis for an instant pop-rap crossover."

David Fricke from Rolling Stone wrote, "In 'I'll Be Missing You', he didn't merely crib from Sting; he took a song about stalking and transformed it into a radiant hymn of brotherly love and a community's loss." Freelance music writer Jeremy Simmonds described it as "somewhat turgid". Ian Hyland from Sunday Mirror gave it nine out of ten, commenting, "Not the greatest rap I've ever heard but this tribute to murdered rapper Notorious B.I.G. is going to be H.U.G.E. In a mish-mash of The Police's 'Every Breath You Take' and John Waite's 'Missing', the highlight is Faith Evans' amazing voice." In March 2024, Forbes magazine ranked "I'll Be Missing You" number 43 in their list of "The 50 Best Songs of the 1990s". Hugh McIntyre named it "a poignant reflection on loss and longing."

"I'll Be Missing You" topped many charts across the world. It reached number one in the United States, the United Kingdom, Australia, Austria, Denmark, Flanders, Germany, Iceland, Ireland, Lithuania, the Netherlands, New Zealand, Norway, Poland, Romania, Spain, Sweden and Switzerland.