H 2 , the smallest and most abundant molecule in the universe, has a perfectly symmetric ground state. What does it take to break this symmetry? Here we show that the inversion symmetry can be broken by absorption of a linearly polarized photon, which itself has inversion symmetry.In particular, the emission of a photoelectron with subsequent dissociation of the remaining H + 2 fragment shows no symmetry with respect to the ionic H + and neutral H atomic fragments. This result is the consequence of the entanglement between symmetric and antisymmetric H + 2 states resulting from autoionization. The mechanisms behind this symmetry breaking are general for all molecules.