List of Billboard Hot 100 number ones of 2005

Published by Billboard magazine, the data are compiled by Nielsen SoundScan based collectively on each single's weekly physical and digital sales, and airplay.

During the year, five acts achieved their first US number-one single, either as a lead artist or featured guest: Mario, Olivia, Gwen Stefani, Carrie Underwood, and Chris Brown.

Other singles with extended chart runs include R&B singer Mario's "Let Me Love You", his best-performing song to date,[10] and rapper 50 Cent's "Candy Shop", each spent nine straight weeks at number one.

Carey is the only artist to have earned two number-one singles in 2005 after "Don't Forget About Us" topped the chart in the final calendar issue of Billboard Hot 100.

"Don't Forget About Us" is Carey's 17th number-one single, placing her third in the list of acts with most number ones in the United States at the time,[3] behind only The Beatles and Elvis Presley.

Mariah Carey spent fifteen weeks atop the Hot 100 in 2005, with fourteen of them being "We Belong Together", which became the second longest running number one single on the chart, following Carey's "One Sweet Day".
A young black man with short black hair, wearing sunglasses and a gray-and-white checked shirt.
R&B singer Mario scored his first number-one single with " Let Me Love You ", which spent at the top spot for nine consecutive weeks, becoming his best-performing single as of 2005.
A woman with blonde curly hair, singing on stage wearing an ornamental military-style jacket and cap.
Singer Gwen Stefani earned her first number one single " Hollaback Girl " in U.S.
A young woman with blonde hair in a red top, holding a microphone and singing with her eyes closed.
Country singer Carrie Underwood earned her first number one single " Inside Your Heaven " in U.S., and stayed at the top for one week.
A man in a red hat, wearing a long red t-shirt over a red long-sleeved shirt, holding a microphone in his right hand.
Singer Chris Brown earned his first number one single " Run It! " in U.S., and stayed at the top for five consecutive weeks.