Ji is the pinyin romanization of a number of distinct Chinese surnames that are written with different characters in Chinese. Depending on the character, it may be spelled Ji, Jí, Ji, or Jì when tone diacritics are used. In Wade–Giles they are romanized as Chi. Languages using the Latin alphabet do not distinguish among the different Chinese surnames, rendering them all as Ji or Chi.

Ji was the ancestral name of the Zhou dynasty which ruled China between the 11th and 3rd centuries BC. Thirty-nine members of the family ruled China during this period while many others ruled as local lords, lords who eventually gained great autonomy during the Spring and Autumn and Warring States periods. Ji is a relatively uncommon surname in modern China, largely because its bearers often adopted the names of their states as new surnames.