Arnold Weinstein (June 10, 1927–September 4, 2005) was an American poet, playwright and librettist, who referred to himself as a "theatre poet".

Weinstein is best known for his collaborations with composer William Bolcom, including the operas McTeague, based on the novel by Frank Norris, A View from the Bridge based on the play by Arthur Miller, and A Wedding, based on the film by Robert Altman. Bolcom described his work with Weinstein as a "true collaboration", and said about him that "He had such a gift for writing words that were singable, and that gave character. He was more influential on a lot of other people than people have taken into account."

With some frequency, Weinstein's work involved adapting the writing of others. He said in an interview in 1992 that "An adaptation gives you a funny kind of limitation that makes it easier to improvise." His early work with Paul Sills, founder of the Second City Theater in Chicago, helped hone those improvisational skills.