瑞利散射（Rayleigh scattering），由英国物理学家约翰·斯特拉特，第三代瑞利男爵（John Strutt, 3rd Baron Rayleigh）的名字命名。它是半径比光或其他电磁辐射的波长小很多的微小颗粒(例如单个原子或分子)对入射光束的散射。瑞利散射在光通过透明的固体和液体时都会发生，但以气体最为显著。

在大气中，太阳光的瑞利散射会导致弥漫天空辐射，这也是天空之所以为蓝色和太阳之所以偏黄色的原因。

瑞利散射适用于尺寸远小于光波长的微小颗粒，和光学的“软”颗粒（即，其折射率接近1）。当颗粒尺度相似或大于散射光的波长时，通常是由米氏散射理论、离散偶极子近似和其它计算技术来处理。

Rayleigh scattering (pronounced /ˈreɪli/ RAY-lee), named after the British physicist Lord Rayleigh (John William Strutt), is the (dominantly) elastic scattering of light or other electromagnetic radiation by particles much smaller than the wavelength of the radiation. Rayleigh scattering does not change the state of material, hence it is a parametric process. The particles may be individual atoms or molecules. It can occur when light travels through transparent solids and liquids, but is most prominently seen in gases. Rayleigh scattering results from the electric polarizability of the particles. The oscillating electric field of a light wave acts on the charges within a particle, causing them to move at the same frequency. The particle therefore becomes a small radiating dipole whose radiation we see as scattered light.