FITS格式文档（全称Flexible Image Transport System）是一种可用于存储、传输、操作科研或其他用途图片的一种数据文档格式，在天文学领域运用尤广。不同于其他图片格式，FITS是专门为科研目的设计的，因此和图片一起存储的还有图片的测光、空间校准等信息。

诸如GIMP，Photoshop以及IrfanView都可以读取到FITS文档中的常用信息，但并不可以完全读取文档中所包含的其它数据信息。

Flexible Image Transport System (FITS) is an open standard defining a digital file format useful for storage, transmission and processing of scientific and other images. FITS is the most commonly used digital file format in astronomy. Unlike many image formats, FITS is designed specifically for scientific data and hence includes many provisions for describing photometric and spatial calibration information, together with image origin metadata.