Sigma Orionis or Sigma Ori is a multiple star system in the constellation Orion, consisting of the brightest members of a young open cluster. It is found at the eastern end of the belt, south west of Alnitak and west of the Horsehead Nebula which it partially illuminates.

Magnitude: 3.77

Distance to Earth: 1,264 light years

Absolute magnitude (M_V): −3.49 (Aa); −2.90 (Ab); −2.79 (B)

Radial velocity (R_v): −29.45 ± 0.45 km/s

Semi-amplitude (K₁) (primary): 72.03 ± 0.25 km/s

Parallax (π): AB: 3.04 ± 8.92 mas; D: 6.38 ± 0.90 mas