Is Labrador retriever a proper noun?

No, "Labrador retriever" is not a proper noun; it is a common noun that refers to a specific breed of dog. Proper nouns are specific names for individual people, places, or organizations, while common nouns refer to general categories. In this case, "Labrador" is often capitalized as it refers to a geographic region, but "retriever" remains lowercase, making the full term a common noun.