Mac Dela is an Irish surname, and may refer to:

• Gann mac Dela, legendary joint High King of Ireland with his brother Genann.
• Genann mac Dela, legendary joint High King of Ireland with his brother Gann.
• Rudraige mac Dela, legendary second High King of Ireland.
• Sengann mac Dela, legendary High King of Ireland.
• Sláine mac Dela, legendary first High King of Ireland.

• John H. Marburger, III
• John H. Marsalis
• John H. Matthews
• John H. McArthur
• John H. McCarthy
• John H. McDonald Journalism Foundation
• John H. McGraw
• John H. McHenry
• John H. McNary
• John H. McWhorter
• John H. Means
• John H. Michaelis
• John H. Mickey
• John H. Milligan
• John H. Mitchell
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• John H. Morehead
• John H. Morgan
• John H. Morrison
• John H. Morrow
• John H. Munroe
• John Hnatyshyn
• John H. Noble
• John Hoad