The Cosmic Background Explorer (COBE) satellite carries three instruments to measure the diffuse infrared and microwave background radiation from the early universe, along with more recent diffuse sources. It was developed by NASA's Goddard Space Flight Center and launched by a Delta rocket on November 18, 1989. It has produced the first measurements of structure in the Big Bang and has shown that the primeval heat radiation has a blackbody spectrum to extraordinary accuracy. The three instruments include a Far Infrared Absolute Spectrophotometer (FIRAS) to cover the range from 100 micrometers to 1 cm wavelength with a 7 degree(s) resolution, a Diffuse Infrared Background Experiment (DIRBE) to map the sky from 1 to 300 micrometers with a 0.7 degree(s) resolution in 10 broad bands, and a Differential Microwave Radiometer (DMR) to map the sky at 31.5, 53, and 90 GHz with a 7 degree(s) resolution. The designs of the instruments and spacecraft are described, and the primary results ar summarized.