The aim of this study was to examine the variations of the Achilles tendon (AT) insertion point into the calcaneal bone (CB) in relation to age and sex using magnetic resonance imaging (MRI). A total of 202 foot and ankle MRIs were reviewed and patients were allocated into three age groups: (I) <18, (II) 18-65, and (III) >65 years. All measurements were obtained on a mid-sagittal scan. The mean measurement values were used to assess the relationships among the AT insertion point, sex, and age. Our main findings revealed that (1) the distance between the most inferior point of the CB and the most inferior part of the AT insertion into the CB increases with age, (2) the height of the AT insertion into the posterior aspect of the CB decreases with age, and (3) the length of the AT insertion into the posterior aspect of the CB decreases with age. The terminal insertion point of the ATon the CB in younger subjects was more distal, whereas in older individuals it was more proximal. These results could help in developing novel strategies for the treatment and prophylaxis of AT injuries in particular patient age groups. Anatomical data about the AT insertion are crucial for developing a computer model of the ATand for biomechanical considerations regarding this tendon. Clin. Anat. 33:545-551, 2020.