HOS may stand for:

  • Hammer of the Scots (board game), a board game
  • Head of State
  • Hearts of Space, a radio program
  • Hellenic Ornithological Society
  • Holt-Oram syndrome
  • Home Ownership Scheme by the Hong Kong Housing Authority
  • Hoosier Southern Railroad by reporting mark
  • Hornbeck Offshore Services by stock ticker symbol
  • Hours of service, laws limiting commercial truck driver working hours
  • Hyper Operating System, a fictional OS designed to run Labors, specifically construction labors, in Patlabor
  • Croatian Defence Forces, abbreviated "HOS" in Croatian, the military arm of the Croatian Party of Rights (1991–1993)
  • Croatian Armed Forces (NDH), abbreviated "HOS" in Croatian, the military of the Independent State of Croat
  • Health Outcomes Survey