SOI might be an acronym or abbreviation for:

  • Silicon on Insulator
  • Signal operating instructions
  • Service-oriented infrastructure
  • Start of injection
  • Southern Oscillation Index
  • Sphere of influence (astrodynamics), a term in astrodynamics
  • Sociosexual Orientation Inventory (SOI)
  • School of Infantry
  • Shadow of Infinity, a Yu-Gi-Oh! Trading Card Game set
  • Sons of Iraq, auxiliary police forces in Iraq
  • Severity of Illness, medical classification
  • Sphere of influence, a term in politics
  • Survey of India
  • Sons of Intellect, a hip-hop group
  • State of Israel
  • Soi, a side street in Thailand
  • The Symphony Orchestra of India
  • Skating tour, Stars on Ice