Siloxides are chemical compounds with the formula R3SiOM, where R is usually an organic group and M is usually a metal cation. Also called silanolates, they are derived by deprotonation of silanols. They also arise by the degradation of siloxanes by base:

Cleavage of cyclic siloxanes affords siloxides:

These anions function as ligands for metal ions, forming complexes similar to metal alkoxides. Sodium trimethylsiloxide is useful for generating metal complexes by salt metathesis reactions. A very bulky siloxide is tert-butyl3SiO−, sometimes called silox.

Siloxides are weaker net donors than alkoxides because pπ-d donation has to compete with backbonding from the oxygen atom into the low-lying Si-C σ* orbitals.