In photography, EOS is a type of Canon brand camera. EOS stands for "Electro Optical System." Eos is also the Greek goddess of dawn, and Canon describes this as being "apropos."
Canon introduced a new line of cameras in 1985, with the intent of creating a highly refined brand of single-lens reflex cameras that focused on performance. This project came to be called EOS, and the cameras in the line were all named "Canon EOS" followed by the model name or number.
The line's namesake, Eos, the goddess of dawn, was an inspiration for Canon's project to produce a new generation of cameras.