This is the last scene in Götterdämmerung (Twilight of the Gods), the last opera in the cycle Der Ring des Nibelungen (The Ring of the Nibelung). The valkyrie-turned-woman Brünnhilde kills herself on the funeral pyre of her beloved Siegfried, freeing the world from the curse of the Ring and killing the Gods in the process. Incidentally: she was the one who had Siegfried killed for betraying her. (If you want to explore more, including how in the first concept of the opera Brünnhilde did not die, wikipedia is your friend.)
Wagner was not a nice guy - notoriously antisemitic, with a tendency to seduce his friends’ wives (plural, yes). But here he gives the world one of the greatest heroines ever, a woman of action and passion alike. It’s hard today to get such great women in fiction. In 1876, I am under the impression that it was almost a scandal.