Logan Pearsall Smith was an American-born essayist and critic.

Smith was an authority on 17th century divines. He was known for his aphorism and epigrams, and his Trivia has been highly rated. He was a literary perfectionist and could take days refining his sentences. With Words and Idioms he became a recognised authority on the correct use of English. He is now probably most remembered for his autobiography Unforgotten Years (1938). He was much influenced by Walter Pater. His followers included Desmond MacCarthy, John Russell, R. C. Trevelyan, and Hugh Trevor-Roper. He was, in part, the basis for the character of Nick Greene / Sir Nicholas Greene in Virginia Woolf's Orlando.

Smith's sister Alys was the first wife of philosopher Bertrand Russell, and his sister Mary married the art historian Bernard Berenson.