A lipogram (from Ancient Greek: λειπογράμματος, leipográmmatos, "leaving out a letter") is a kind of constrained writing or word game consisting of writing paragraphs or longer works in which a particular letter or group of letters is avoided — usually a common vowel, and frequently "E", the most common letter in the English language.

Writing a lipogram is a trivial task for uncommon letters like "Z", "J", "Q", or "X", but it is much more difficult for common letters like "E", "T" or "A". Writing this way, the author must omit many ordinary words. Grammatically meaningful and smooth-flowing lipograms can be difficult to compose.

A pangrammatic lipogram or lipogrammatic pangram is a text that uses every letter of the alphabet except one, e.g. "The quick brown fox jumped over the lazy dog", which omits "S."

One of the earliest and most remarkable examples of lipogram is Ernest Vincent Wright's novel Gadsby (1939), which has over 50,000 words but not a single letter "E". Wright's self-imposed rule prohibited such common English words as "the" and "he", plurals in "-es", past tenses in "-ed", and even abbreviations like "Mr." (for "Mister") or "Bob" (for "Robert"). Yet the narration flows fairly smoothly, and the book was praised by critics for its literary merits.