The ARIA Singles Chart ranks the best-performing singles in Australia. Its data, published by the Australian Recording Industry Association, is based collectively on the weekly physical and digital sales and streams of singles. In 2021, eight songs have reached number one; the first, "Mood" by 24kGoldn featuring Iann Dior, returned to the top on the first chart of the year after spending nine weeks atop the chart in 2020. Seven artists, Olivia Rodrigo, Glass Animals, Daniel Caesar, Giveon, the Kid Laroi, Russ Millions, and Tion Wayne reached the top for the first time. Olivia Rodrigo has achieved two number ones on the chart in 2021.