Ireland reached 312-3 in their 50 overs on Monday thanks to Hunter's unbeaten 121 off 127 deliveries, a knock that included eight fours. Zimbabwe managed 227-8 in reply as the visitors claimed a 3-1 series victory.
Belfast schoolgirl Hunter eclipsed India's Mithali Raj, who held the record after her unbeaten 114 against Ireland in a one-day international (ODI) in June 1999 at the age of 16 years and 205 days, according to ESPNCricinfo.
Pakistan's Shahid Afridi is the youngest man to score an international century. He had hit 102 runs against Sri Lanka in an ODI in 1996 at the age of 16 years and 217 days.