XO

XO may refer to:

• XO, a grade of cognac, meaning "extra old"
• XO, the IATA code for Spain's LTE International Airways
• XO Communications, a telecom company
• XO sauce, a spicy seafood sauce
• XO Telescope and its related exo-planet survey
• XO-1 laptop, produced by the One Laptop per Child association
• XO-3 laptop, next generation One Laptop per Child laptop
• Crystal oscillator, an electronic circuit that uses the mechanical resonance of a vibrating crystal to create an electrical signal with a precise frequency
  • XO, the now-deprecated abbreviation for crystal oscillators on electrical schematic diagrams
• Executive officer in the military
• Executive order (disambiguation), an edict by a member of the executive branch of a government
• Eastern Orthodox Christianity (from the Greek: Χριστιανός Ορθόδοξος, Xristianos Orthodoksos)
• Hugs and kisses, sometimes written as a sequence of XOs
• Xanthine oxidase, an enzyme that catalyzes the oxidation of hypoxanthine to xanthine