弗罗因德利希方程（英语：Freundlich equation，或称为弗罗因德利希吸附等温线）是吸附等温线其中的一种，吸附等温线创建了吸附在吸附剂上溶质的浓度与在液相中溶质的浓度两者之间的关系。1909年，赫伯特·弗罗因德利希提出了一个经验表达式用以表示每单位质量固体吸附剂上已吸附气体的量与气体压力这两者之间的等温变动。该方程亦被称为弗罗因德利希吸附等温线或弗罗因德利希吸附方程。大体上来说，有两种类型广为接受的吸附等温线：弗罗因德利希吸附等温线与朗缪尔吸附等温线。将被吸附物质的质量对温度作图，就可以得到吸附随温度的变化情况。

The Freundlich equation or Freundlich adsorption isotherm, an adsorption isotherm, is an empirical relation between the concentration of a solute on the surface of an adsorbent to the concentration of the solute in the liquid with which it is in contact. In 1909, Herbert Freundlich gave an expression representing the isothermal variation of adsorption of a quantity of gas adsorbed by unit mass of solid adsorbent with pressure. This equation is known as Freundlich Adsorption Isotherm or Freundlich Adsorption equation. As this relationship is entirely empirical, in the case where adsorption behavior can be properly fit by isotherms with a theoretical basis, it is usually appropriate to use such isotherms instead (see for example the Langmuir and BET adsorption theories).