在热力学里，吉布斯能（英语：Gibbs energy），又称吉布斯自由能、吉布斯函数（Gibbs function）、自由焓（free enthalpy），常用英文本母「」标记。吉布斯能是国际化学联会建议采用的名称。吉布斯能是描述系统的热力性质的一种热力势，定义为

其中，是系统的内能，是绝对温度，是熵，是压强，是体积，是焓。

假设在等温等压状况下，一个热力系统从良好定义初态变换到良好定义终态，则其吉布斯能减少量必定大于或等于其所做的非体积功；假若这变换是可逆过程，则其吉布斯能减少量等于其所做的非体积功。所以，这热力系统所能做的最大非体积功是其吉布斯减少量。

In thermodynamics, the Gibbs free energy (IUPAC recommended name: Gibbs energy or Gibbs function; also known as free enthalpy to distinguish it from Helmholtz free energy) is a thermodynamic potential that measures the maximum or reversible work that may be performed by a thermodynamic system at a constant temperature and pressure (isothermal, isobaric). Just as in mechanics, where potential energy is defined as capacity to do work, similarly different potentials have different meanings. The Gibbs free energy (kJ in SI units) is the maximum amount of non-expansion work that can be extracted from a thermodynamically closed system (one that can exchange heat and work with its surroundings, but not matter); this maximum can be attained only in a completely reversible process. When a system changes from a well-defined initial state to a well-defined final state, the Gibbs free energy change ΔG equals the work exchanged by the system with its surroundings, minus the work of the pressure forces, during a reversible transformation of the system from the initial state to the final state.