Quadruple bonding in heavier main group elements is not known albeit having four valence orbitals accessible for bonding. Here we report the unprecedented quadruple bonding between a silicon atom and a transition metal fragment in the 1A1 electronic ground state of C3v symmetric SiRu(CO)3 based on high level theoretical calculations. Various bonding analyses reveal the nature of the Si[quadruple bond, length as m-dash]Ru quadruple bonding interaction, which involves one usual Si-Ru σ bond, two usual Si-Ru π bonds and one additional Si → Ru dative σ bond.