Abstract Context Minipuberty, a period of a transient activation of the hypothalamic-pituitary-gonadal (HPG) axis in both sexes, enables evaluation of gonadal function in infants suspected of hypogonadism. However, female minipuberty remains poorly elucidated. Objective We aimed to establish continuous reference ranges for the most commonly used reproductive hormones and to evaluate the dynamics of the HPG axis in females aged 0 to 1 year. Design The COPENHAGEN Minipuberty Study (ClinicalTrials.gov ID: NCT02784184), a longitudinal, prospective cohort study. Setting Healthy infants from Copenhagen. Patients or Other Participants A total of 98 healthy, term female infants followed with 6 examinations including venipuncture during the first year of life. Intervention(s) None. Main Outcome Measure(s) Serum concentrations of LH, FSH, inhibin B, anti-Müllerian hormone (AMH), estrone (E1), estradiol (E2), and SHBG were quantified using highly sensitive methods in 266 serum samples. Results Reference ranges were established for LH, FSH, inhibin B, AMH, E1, E2, and SHBG. Two peaks were observed in normalized mean curves for all hormones. The first peaks were timed around postnatal days 15 to 27 followed by a general nadir for all hormones around days 58 to 92. The second peaks occurred around days 107 to 125 for inhibin B, AMH, E1, E2, and SHBG and days 164 to 165 for LH and FSH. Conclusions We present age-related, continuous reference ranges of the most commonly used reproductive hormones and present novel data revealing a biphasic and prolonged female minipuberty. ClinicalTrials.gov ID NCT02784184