* Ocicat: Known for their striking spotted pattern resembling that of an ocelot.
* Oriental: A group of shorthaired cats with pointed patterns and a range of colors and markings.
* Ojos Azules: A breed known for their striking blue eyes and white fur.
It's worth noting that many cat breeds have variations or are recognized by different cat registries, so there might be some lesser-known breeds starting with "O" out there!