Original: Die Walküre (The Valkyrie) is the second of the four operas that comprise Der Ring des Nibelungen (The Ring of the Nibelung), by Richard Wagner.
Simplified: Die Walküre (The Valkyries) is an opera by Richard Wagner. It is the second of the four operas that together tell a story called Der Ring des Nibelungen (The Ring of the Nibelung). The whole cycle is called Der Ring des Nibelungen.