A single covalent bond is a covalent bond consisting of one shared pair of electrons between two atoms. It is the simplest and most common covalent bond and allows free rotation about the bond axis. The Cl–Cl bond in chlorine (Cl₂) is a single bond, in contrast to the double and triple bonds, which share more than one pair.

单键是由两个原子之间共享一对电子组成的共价键。它是最简单也最常见的共价键,并允许绕键轴自由旋转。氯(Cl₂)中的 Cl–Cl 键是单键;与之相对的是共享不止一对电子的双键和叁键。