The Wagner tuba is an uncommon brass instrument that resembles both the French horn and the tuba. It was originally created for Richard Wagner's operatic cycle Der Ring des Nibelungen. Since then, other composers have written for it, including Anton Bruckner, Arnold Schoenberg, Richard Strauss, Igor Stravinsky, and Edgard Varese. The euphonium is sometimes used as a substitute when a Wagner tuba can not be obtained.

Wagner was inspired to invent this instrument after a brief visit to Paris in 1853, when he had dropped by the shop of Adolphe Sax, the inventor of the saxophone. Wagner wanted an instrument that could intone the Walhalla motif somberly like a trombone but less incisive like a horn.

The Wagner tuba comes in two sizes, tenor in B-flat and bass in F, and both are transposing instruments. The tenor tuba's written range is from the C below middle C to the G a twelfth above middle C, and it sounds a major second lower than written. The bass tuba's written range is from the F a twelfth below middle C to the D a ninth above middle C, and it sounds a perfect fifth lower than written.

The sound of the Wagner tuba is mellower than that of the horn and sounds more distant, yet also more focused. Bruckner generally uses them for pensive melodic passages at piano to pianissimo dynamics. They can hold their own in a forte tutti, of course, but Bruckner generally gives them sustained tones rather than melodic motifs in such passages. In Bruckner's Eighth and Ninth Symphonies, the four Wagner tubas are played by four players who alternate between playing horn and Wagner tuba, which is the same procedure Wagner used in the Ring. This change is simplified by the horn and Wagner tuba using the same mouthpiece.