What's Opera, Doc? is a 1957 American Warner Bros. Merrie Melodies cartoon directed by Chuck Jones and written by Michael Maltese. The short was released on July 6, 1957, and stars Bugs Bunny and Elmer Fudd.

The story features Elmer chasing Bugs through a parody of 19th-century classical composer Richard Wagner's operas, particularly Der Ring des Nibelungen (The Ring of the Nibelung), Der Fliegende Holländer (The Flying Dutchman), and Tannhäuser. It borrows heavily from the second opera in the "Ring Cycle" Die Walküre, woven around the typical Bugs–Elmer feud. Most of the dialogue is performed in recitative. The short marks the final appearance of Elmer Fudd in a Chuck Jones cartoon.

It has been widely praised in the animation industry as the greatest animated cartoon that Warner Bros. ever released, and it has been ranked as such in the top 50 animated cartoons of all time. In 1992, the Library of Congress deemed it "culturally, historically or aesthetically significant" and selected it for preservation in the National Film Registry.