A mullion is a structural element which divides adjacent window units.

Mullion may also refer to:

• Annabel Mullion (born 1969), English actress
• Mullion (geology), a reworked boudin, geological term for structures formed by extension
• Mullion, Cornwall, a village and parish in Cornwall, England
• Mullion Cove, a harbour and cove in Cornwall
• Mullion Creek, Australia
• Mullion Island, a small island in Mount's Bay, Cornwall

• 1971 World Fencing Championships
• 1971 World Figure Skating Championships
• 1971 World Ice Hockey Championships
• 1971 world jamboree
• 1971 World Judo Championships
• 1971 World Modern Pentathlon Championship
• 1971 World Modern Pentathlon Championships
• 1971 World Wrestling Championships
• 1971 WS
• 1971 Yankee 400
• 1971 Úrvalsdeild
• 1971–1972 United States network television schedule
• 1971–72 1.Lig
• 1971–72 ABA season
• 1971–72 A Group
• 1971–72 Albanian Superliga
• 1971–72 All-Ireland Senior Club Hurling Championship
• 1971–72 Australian region cyclone season
• 1971–72 Austrian football championship
• 1971–72 Bahraini Premier League
• 1971–72 Baltimore Bullets season
• 1971–72 Belgian First Division
• 1971–72 Blackpool F.C. season
• 1971–72 Buffalo Braves season
• 1971–72 Buffalo Sabres season