OU or Ou or ou may stand for:
Outlook.com is a web-based suite of webmail, contacts, tasks, and calendaring services from Microsoft.
Outsourcing is an agreement in which one company hires another company to be responsible for a planned or existing activity that is or could be done internally,
An outlaw motorcycle club, is a motorcycle subculture that has its roots in the immediate post-World War II era of North American society.
The Outer Hebrides (), also known as the Western Isles (Scottish Gaelic: Na h-Eileanan Siar [nə ˈhelanən ˈʃiəɾ] or Na h-Eileanan an Iar [nəˈhelanən əˈɲiəɾ]), Innse Gall ("islands of the strangers") or the Long Isle or the Long Island (Scottish Gaelic: An t-Eilean Fada), is an island chain off the west coast of mainland Scotland.
Outlander is a drama television series based upon author Diana Gabaldon's historical time travel book series of the same name.
Outer space, or just space, is the expanse that exists beyond the Earth and between celestial bodies. Outer space is not completely empty—it is a hard vacuum containing a low density of particles, predominantly a plasma of hydrogen and helium, as well as electromagnetic radiation, magnetic fields, neutrinos, dust, and cosmic rays.