类氢原子（hydrogen-like atom）是只拥有一个电子的原子，与氢原子同为等电子体，例如，He, Li, Be与B等等都是类氢原子，又称为「类氢离子」。类氢原子只含有一个原子核与一个电子，是个简单的二体系统，系统内的作用力只跟二体之间的距离有关，是反平方连心力。这反平方连心力二体系统不需再加理想化，简单化。描述这系统的（非相对论性的）薛丁格方程序有解析解，也就是说，解答能以有限数量的常见函数来表达。满足这薛丁格方程序的波函数可以完全地描述电子的量子行为。在量子力学里，类氢原子问题是一个很简单，很实用，而又有解析解的问题。所推演出来的基本物理理论，又可以用简单的实验来核对。所以，类氢原子问题是个很重要的问题。

A hydrogen-like ion is any atomic nucleus with one electron and thus is isoelectronic with hydrogen. Except for the hydrogen atom itself (which is neutral), these ions carry the positive charge , where is the atomic number of the atom. Examples of hydrogen-like ions are He, Li, Be and B. Because hydrogen-like ions are two-particle systems with an interaction depending only on the distance between the two particles, their (non-relativistic) Schrödinger equation can be solved in analytic form, as can the (relativistic) Dirac equation. The solutions are one-electron functions and are referred to as hydrogen-like atomic orbitals.