List of Billboard Hot 100 number-one singles of 1981

These are the Billboard Hot 100 number-one hits of 1981. The longest running number-one single of 1981 is "Physical" by Olivia Newton-John which stayed at the top of the chart for six weeks in 1981 and then for four additional weeks in 1982, with a total of 10 weeks at number-one. This also makes "Physical" the longest running number-one single of the 1980s.

That year, 10 acts hit number one for the first time, such as Kool & the Gang, Dolly Parton, Eddie Rabbitt, REO Speedwagon, Sheena Easton, Kim Carnes, Stars on 45, Air Supply, and Rick Springfield. Lionel Richie, already having hit number one with The Commodores, also receives his first number one song as a solo act. Blondie and Daryl Hall and John Oates were the only acts to hit number one more than once, with both acts hitting twice.

"9 to 5" by Dolly Parton reached the top spot for two non-consecutive weeks on February 21 and March 14, 1981, sandwiched with two weeks of "I Love a Rainy Night" by Eddie Rabbitt. Sheena Easton's No. 1 hit "9 to 5" was retitled "Morning Train" to avoid confusion.