A SGY file is a data file saved in the SEG-Y (Society of Exploration Geophysicists) format. It contains geophysical data in binary and textual format, which includes the coordinates of reflected seismic waves. SGY files may store sweep frequency, types, and length, impulse signal polarity, projection zone and method, and other metadata.

SGY files are created by various seismic tools used to map and measure subsurface properties of the earth by sending a controlled energy and recording reflected waves, much like sonar devices. The SGY files can then be opened and viewed using various programs, such as Geopsy, and kogeo. The SEG-Y format evolved from the SEG format, which was originally published in 1975 and is widely used in the geophysical industry. NOTE: SEG files may also be saved as .SEGY files.