The Canon EOS (Electro-Optical System) autofocus 35 mm film and digital SLR camera system was introduced in 1987 with the Canon EOS 650 and is still in production as Canon's current DSLR system. The acronym EOS was chosen for Eos, the Titan Goddess of dawn in Greek mythology, and is often pronounced as a word (i.e., UK: /ˈiː.ɒs/, US: /ˈiː.ɑːs/), although some spell out the letters, reading it as an initialism.

It competes primarily with the Nikon F series and its successors, as well as autofocus SLR systems from Olympus Corporation, Pentax, Sony/Minolta, and Panasonic/Leica. Between 2006 and 2008, Canon's market share in DSLR cameras decreased from nearly 50% worldwide to near-parity with Nikon DSLRs, at 38% and 37%, respectively. While in 2010, Canon rose to a share of 44.5% in the DSLR market, jumping far ahead of Nikon's 29.8% and Sony's 11.9%, becoming the worldwide leader of DSLR manufacturers.