在光学里，菲涅耳衍射（Fresnel diffraction）指的是光波在近场区域的衍射。菲涅耳衍射积分式可以用来计算光波在近场区域的传播，因法国物理学者奥古斯丁·菲涅耳而命名，是基尔霍夫衍射公式的近似。

从每一个光学系统特征的菲涅耳数，可以辨别光波传播的区域是近场还是远场。设想光波入射于任意孔径，对于这光学系统，菲涅耳数定义为

其中， 是孔径的尺寸， 是孔径与观察屏之间的距离， 是入射波的波长。

假若 ，则衍射波是处于近场，可以使用菲涅耳衍射积分式来计算其物理性质。

In optics, the Fresnel diffraction equation for near-field diffraction, is an approximation of Kirchhoff-Fresnel diffraction that can be applied to the propagation of waves in the near field. It is used to calculate the diffraction pattern created by waves passing through an aperture or around an object, when viewed from relatively close to the object. In contrast the diffraction pattern in the far field region is given by the Fraunhofer diffraction equation.