A Variorum is a work that collates all known variants of a text. It is a work of textual criticism, whereby all variations and emendations are set side by side so that a reader can track how textual decisions have been made in the preparation of a text for publication. The Bible and the works of William Shakespeare have often been the subjects of variorum editions, although the same techniques have been applied with less frequency to many other works.

A variorum of the Bible has been produced at various times in history and of various scopes. Documenting each line of text with all variants in wording, from all known source documents, presented chronologically, helps translators of the Bible establish primacy and prevalence of various line readings.

There have also been noteworthy variorums of the works of William Shakespeare, including the readings of all quartos and folios; the textual decisions, or choices, of past editors; and a compilation of all critical notes. Variorum editions help editors and scholars understand the historical evolution of the Shakespeare texts, as well as to decode dubious lines and decide upon most likely authorial intent.