Christina Hammer (born 16 August 1990) is a Kazakhstani-German boxer. As a professional, she is a multiple-time world champion in two weight classes, having held the WBO female middleweight title from 2010 to 2019, becoming the youngest boxer in history to win a WBO title. Previously she held the WBC female middleweight title between 2016 and 2018, and the WBO female super-middleweight title in 2013. She also challenged once for the WBO female light-middleweight title in 2014 and once for the undisputed female middleweight championship against Claressa Shields in 2019. In February 2021, she returned to the amateur ranks with the intention of competing at the Tokyo Olympics.