Millennium is the third album (second in the United States) by the American boy band the Backstreet Boys. It was a highly anticipated follow-up to both their U.S. debut album, and their second internationally released album. It was their first album to be released in both the U.S. and internationally in the same form, at the same time.

In the United States, it holds the record for most shipments in one year, with 11 million in 1999. It was nominated for five Grammy Awards and spawned four Top 40 singles, including the single "I Want It That Way". Three of the singles, "I Want It That Way", "Larger than Life" and "Show Me the Meaning of Being Lonely", became some of their most successful and remembered hits of all time, with "I Want It That Way" becoming their biggest hit to date. Millennium has since become one of the best-selling albums of all time, selling over 30 million copies worldwide.