In chemistry, a lyate ion is the anion derived by the deprotonation of a solvent molecule.^[1] For example, a hydroxide ion is formed by the deprotonation of water, and methoxide (CH₃O⁻) is the anion formed by the deprotonation of methanol.

Its counterpart is a lyonium ion, the cation formed by the protonation of a solvent molecule.

Lyonium and lyate ions, resulting from molecular autoionization, contribute to the molar conductivity of protolytic solvents.