"Mo Money Mo Problems" is a single by The Notorious B.I.G., the second single from his album Life After Death. Released posthumously, the single topped the Billboard Hot 100 for two weeks in 1997, replacing "I'll Be Missing You" from the chart, Puff Daddy's tribute to the rapper's death himself. The song is Notorious B.I.G.'s second posthumous number one single, following "Hypnotize", making him the only artist in Hot 100 history to have two #1 singles posthumously. It was the sixth song to hit #1 posthumously for a credited artist. The song was nominated for the 1998 Grammy Award for Best Rap Performance by a Duo or Group.

The song features guest vocals from Mase and Sean "Puff Daddy" Combs. The instrumental contains a sample of the low pitched version of the Diana Ross song "I'm Coming Out", including backing vocals which repeat the title of that song. The refrain of the song was sung by Kelly Price. Based on airplay and chart success the song is considered one of the most popular singles in hip hop history.

"Mo Money Mo Problems" was able to top the Billboard Hot 100 for two weeks giving Biggie his second number 1 hit in the US. The song hit number 1 after he had died. It was preceded by "I'll Be Missing You" by Puff Daddy featuring 112 and Faith Evans (meaning that Puff Daddy spent 13 weeks in a row at the top of the Hot 100) and was succeeded by "Honey" by Mariah Carey, which was also co-produced by Puff Daddy. The single reached #6 in the UK charts.

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