Res or RES may refer to:

• Russian and Eurasian Security Network
• Spanish Supercomputing Network (Red Española de Supercomputación)

• RES - The School for Renewable Energy Science
• US Renewable Electricity Standard
• Renewable Energy Systems, a UK company

• Residue (complex analysis) function

• Reticuloendothelial system, in anatomy

• Répertoire d'Épigraphie Sémitique, a journal publishing Semitic language inscriptions

• Entity (disambiguation)
• Object (philosophy)
• The first word of several Latin phrases:
  • Res divina (service of the gods)
  • Res cogitans, Descartes' mental world
  • Res communis, a thing that is owned in common
  • Res extensa, Descartes' physical world
  • Res gestae (Things done)
  • Res inter alios acta (A thing done between others)
  • Res ipsa loquitur (The thing speaks for itself)
  • Res judicata (A matter [already] judged)
  • Res nullius (An unowned thing)
  • Res publica (A public thing), the origin of the word republic

• Rail Express Systems
• Railway Enthusiasts Society, New Zealand
• Royal Economic Society, UK
• Royal Entomological Society

• Reservoir railway station, Melbourne
• Resistencia International Airport (IATA airport code: RES)

• Res (singer), American singer

• RES (magazine), bimonthly

• "R.E.S.", a song by Cardiacs from The Seaside
• "The Res", a song by the American band Bright from their self-titled album

• RE5 (disambiguation)
• Rez (disambiguation)