Billy Kelly may refer to:

• Billy Kelly (baseball) (1886–1940), American baseball player
• Billy Kelly (boxer) (1932–2010), boxer from Derry, Northern Ireland
• Billy Kelly (horse), an American Thoroughbred racehorse

• Triarii
• Triariia
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• Triaristellina anaristella
• Triarius (disambiguation)
• Triarius (tree)
• Triart Design Marker
• Triarthria
• Triarthria setipennis
• Triaryl
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• Trias (disambiguation)
• Trias (genus)
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• Trias (plant)
• Triassic Attack
• Triassic dinosaurs
• Triassic Extinction
• Triassic-Jurassic extinction event
• Triassic Nunatak
• Triatec
• Tri-athlete
• Triathlon Alpe d'Huez
• Triathlon at the 2002 Central American and Caribbean Games