电感（Inductance）是闭合回路的一种属性，即当通过闭合回路的电流改变时，会出现电动势来抵抗电流的改变。如果这种现象出现在自身回路中，那么这种电感称为自感（self-inductance），是闭合回路自己本身的属性。假设一个闭合回路的电流改变，由于感应作用在另外一个闭合回路中产生电动势，这种电感称为互感（mutual inductance）。电感以方程序表达为

其中，是电动势，是电感，是电流，是时间。

术语「电感」是1886年由奥利弗·赫维赛德命名。通常自感是以字母「L」标记，这可能是为了纪念物理学家海因里希·楞次的贡献。互感是以字母「M」标记，是其英文（Mutual Inductance）的第一个字母。采用国际单位制，电感的单位是亨利（henry），标记为「H」，是因美国科学家约瑟·亨利命名。1 H = 1 Wb/A。

In electromagnetism and electronics, inductance is the property of an electrical conductor by which a change in current through it induces an electromotive force in both the conductor itself and in any nearby conductors by mutual inductance.

These effects are derived from two fundamental observations of physics: a steady current creates a steady magnetic field described by Oersted's law, and a time-varying magnetic field induces an electromotive force (e.m.f) in nearby conductors, which is described by Faraday's law of induction. According to Lenz's law, a changing electric current through a circuit that contains inductance induces a proportional voltage, which opposes the change in current (self-inductance). The varying field in this circuit may also induce an e.m.f. in neighbouring circuits (mutual inductance).