Ibid. is an abbreviation for the Latin word ibīdem, meaning "in the same place", commonly used in an endnote, footnote, bibliography citation, or scholarly reference to refer to the source cited in the preceding note or list item. This is similar to Idem, literally meaning "the same", abbreviated id., which is commonly used in legal citation.

Ibid. may also be used in the Chicago (name-date) system for in-text references where there has been a close previous citation from the same source material. The previous reference should be immediately visible, e.g. within the same paragraph or page.

Some academic publishers now prefer that "ibid." not be italicised, as it is a commonly found term. Usage differs from style or citation guides as to whether ibid should be suffixed with a full stop. For example, Oxford Standard for Citation of Legal Authorities omits full stops and does not capitalise, while the Economist Style guide uses a lower case starting letter with ending full stop.