The first model was presented at photokina in Cologne in 1972 and was called the Olympus M-1. Thirteen years earlier, the release of the Nikon F had made the 35 mm SLR the standard choice for professionals accustomed to Leica and other rangefinders, but it had driven the market towards heavy and bulky cameras. The Olympus M-1 changed this and with it began a reduction of size, weight and noise of the 35 mm SLRs. It was designed by a team led by Yoshihisa Maitani, who had already created the Pen and Pen F cameras, noted for their compactness.

Since Leica's flagship rangefinder cameras are known as the M Series, Leica complained about the name of the M-1, forcing Olympus to rename it as the OM-1 to further clarify between the brands.

The OM-1 is an all-mechanical SLR. It has a large viewfinder with interchangeable screens but a fixed prism. It also has a through-the-lens exposure meter controlling a needle visible in the viewfinder. It has a compact body, essentially retained on later models. The shutter speed dial is located around the lens mount, which allows photographers to keep the camera at the eye between shots more easily than SLRs with the dial located on the top plate.