The 2021 Japan National Fertility Survey is the 16th survey in the series. Its primary aim is to discover situations and backgrounds to marriage and fertility of married couples and to gather essential data for the development of relevant policies and future population projections. Originally slated for June 2020, this iteration was postponed to 2021 due to the COVID-19 pandemic, marking a five-year interval since the previous survey in 2015. The survey includes two distinct parts: one focusing on single individuals aged 18 to 54 and another on married couples where the wives are under 55 years old, with the latter's responses being collected from the wives. 7,826 valid responses were gathered for the singles survey, and 6,834 valid responses were gathered for the survey of married couples.