Disulfur dioxide, dimeric sulfur monoxide or SO dimer is an oxide of sulfur. The molecule is unstable with a lifetime of a few seconds. It is an asymmetric top molecule. The molecule adopts cis-planar structure with C_2v symmetry with the two sulfur atoms joined. The shape is the same as the tetrasulfur molecule S₄. The S-O bond length is 145.8 pm, shorter than in the sulfur monoxide monomer, and the S-S bond length is 202.45 pm. The OSS angle is 112.7°. S₂O₂ has a dipole moment of 3.17 D.