The women's lightweight boxing event at the 2020 Summer Olympics took place between 27 July and 8 August 2021 at the Ryōgoku Kokugikan. 20 boxers from 20 nations competed.

The team of the Olympic Federation of Ireland, which competed at the 2020 Summer Olympics in Tokyo, represented athletes from both the Republic of Ireland and those from Northern Ireland who choose it instead of the Great Britain and Northern Ireland team. Originally scheduled to take place from 24 July to 9 August 2020, the Games were postponed to 23 July to 8 August 2021, due to the COVID-19 pandemic. It was the team's twenty-second appearance at the Summer Olympics, having attended every edition since 1924 except the 1936 Summer Olympics in Germany.