Duncan Forbes may refer to:

• Duncan Forbes of Culloden (politician, died 1654), Scottish politician and burgh commissioner for Inverness
• Duncan Forbes of Culloden (politician, born 1644) (1644–1704), Scottish politician and supporter of the House of Hanover, grandson of the above
• Duncan Forbes of Culloden (judge, born 1685) (1685–1747), Scottish politician and judge, son of the above
• Duncan Forbes (linguist) (1798–1868), Scottish linguist
• Duncan Forbes (historian) (1922–1994), Scottish historian
• Duncan Forbes (footballer) (1941–2019), Scottish footballer
• Duncan Forbes (poet) (born 1947), British poet