SO2 or SO₂ may refer to:

• Sulfur dioxide (SO₂), a colorless gas with a pungent smell
  • Sulfonyl group (R-SO₂-R), a functional group found primarily in sulfones, or a substituent
• SO(2), special orthogonal group of degree 2 in mathematics
• Oxygen saturation (SO₂), the concentration of oxygen dissolved in a medium
• S2 (star) or S0–2, a star near the central black hole at the center of the Milky Way
• 2015 SO₂ or 2015 SO2, an Aten asteroid

• SO2, a staff officer of the second class, often a commissioned officer of lieutenant commander, major or squadron leader rank
• SO2, a London Metropolitan Police Specialist Operations command division
• Special Operations 2 – Operational, of the British, World War II Special Operations Executive

• SO2 (album), a 2010 album by Shinichi Osawa

• Oxygen saturation (medicine) (SaO₂, SvO₂, StO₂, SpO₂)
• All pages with titles beginning with SO2
• All pages with titles containing SO2
• Soso (disambiguation)
• Soo (disambiguation)
• SO (disambiguation)