Although serum ferritin is considered a reliable indicator of iron stores, there are little data documenting the prevalence of low ferritin in representative samples of young women. Aims To estimate the prevalence of low ferritin and to identify factors associated with low ferritin in young Australian women. Methods Women, aged 18‐39 years, living in the eastern states of Australia were recruited by email to a cross‐sectional, online questionnaire‐based study between November 2016 and July 2017. Participants not pregnant, breast feeding, taking hormonal contraception, using assisted reproduction or postmenopausal were invited to provide a blood sample. Results Of the 3,689 invited participants, 761 (23.1%) provided a sample and 736 women, mean (SD) age 31.7 (±5.6) years, were included in the analyses. The overall prevalence of serum ferritin <30μg/L was 34.8% (95%CI 31.4‐38.3%), with 41.4% (35.1‐48.0%) in NSW, 31.5% (26.4‐37.1%) in Victoria and 32.6% (26.8‐39.0%) in Queensland. Serum ferritin <30μg/L was positively associated with the reporting of >2 days of heavy menstrual bleeding (AOR 1.73, 95%CI 1.15‐2.59), living in New South Wales (AOR 1.57, 95%CI 1.07‐2.30), not working outside home (AOR 1.58, 95%CI 1.01‐2.49), and inversely associated with never experiencing heavy menses (AOR 0.46, 95%CI 0.23‐0.93) and obesity (AOR 0.32, 95%CI 0.21‐0.50). Conclusions This study demonstrates that serum ferritin below 30μg/L is common amongst young Australian women. Health care professionals should note the association between low ferritin and heavy bleeding.