溶解热指在一定温度及压力下(通常是温度为298K，压力为100kPa的标准状态)，一定质量的溶质溶解于溶剂中产生的热效应。等于一摩尔的溶质溶解在大体积的溶剂时所发出或吸收的热量。在等压状态下，溶解热等同于焓值的变化，因此也被称为溶解焓。

溶质的量为1摩尔时的溶解热叫做摩尔溶解热。

由于在纯溶剂中或某一浓度的溶液中溶解相同物质的溶质严格说其溶解热是不一样的：

溶解热对研究溶液性质和化工生产均有指导作用。

The enthalpy of solution, enthalpy of dissolution, or heat of solution is the enthalpy change associated with the dissolution of a substance in a solvent at constant pressure resulting in infinite dilution.

The enthalpy of solution is most often expressed in kJ/mol at constant temperature. The energy change can be regarded as being made of three parts, the endothermic breaking of bonds within the solute and within the solvent, and the formation of attractions between the solute and the solvent. An ideal solution has a null enthalpy of mixing. For a non-ideal solution it is an excess molar quantity.