An alkoxide ion is the conjugate base of an alcohol, written R–O⁻, formed when the alcohol loses the proton from its hydroxyl group. It matters because the alkoxide is a strong base and a good nucleophile, used to bring about eliminations and to make ethers. As the conjugate base of a weak acid (an alcohol), it is itself strongly basic, in contrast to the much weaker carboxylate ion, whose negative charge is stabilised by resonance.

烷氧负离子是醇的共轭碱,写作 R–O⁻,由醇失去其羟基上的质子而生成。它之所以重要,是因为烷氧负离子是强碱和良好的亲核试剂,可用于实现消除反应和制备醚。作为弱酸(醇)的共轭碱,它本身碱性很强,这与碱性弱得多的羧酸根离子形成对照,后者的负电荷因共振而稳定。