热力学极限是指粒子数（或体积）趋向无穷大时的极限。一般宏观物体包含了10个粒子，可以认为是满足热力学极限的。

热力学极限是一个统计物理中的常用假设，很多结论只有在热力学极限下才会成立，例如：杨振宁和李政道证明相变只有在热力学极限下才会发生；熵与能量等物理量的广延性只有在热力学极限下才成立。

热力学极限也是玻尔兹曼统计的假设前提之一。

The thermodynamic limit, or macroscopic limit, of a system in statistical mechanics is the limit for a large number N of particles (e.g., atoms or molecules) where the volume is taken to grow in proportion with the number of particles. The thermodynamic limit is defined as the limit of a system with a large volume, with the particle density held fixed.