Alexander Horn may refer to:

• Alexander Horn (1762–1820), secret agent monk
• Alex Horn (1929–2007), cult leader, playwright and actor
• Alexander horn aka Alex horn, musical instrument
• Alexander horned sphere, mathematical concept
• Alexander Horne, Governor of the Isle of Man 1713–1723
• Alex Horne (born 1978), British comedian
• Horns of Alexander, a mythological motif associated with Alexander the Great