List of number-one singles of 2021 (Ireland)

The list of number-one singles in Ireland during 2021 is compiled by the Official Charts Company (OCC) on behalf of the Irish Recorded Music Association (IRMA). The chart week runs from Friday to Thursday. The official Irish Singles Chart ranks the best-performing singles in Ireland each week, based on sales and streaming activity. This list documents the songs that reached the top position on this chart throughout the year 2021. It includes the artist(s) who performed the song, the date the song reached number one, and the number of weeks the song remained at the top of the chart, if applicable. Any notable facts or records associated with these number-one singles may also be included.