O
- OAC - Oakland, California Coliseum Airport
- OBK - Overbrook, Philadelphia, Pennsylvania- inactive
- OCA - Ocala, Florida
- OCM - Ocean City, Maryland
- OGD - Ogden, Utah
- OGW - Okanogan, Washington
- OKC - Oklahoma City, Oklahoma
- OKE - Okeechobee, Florida
- OKJ - Oakland, California Jack London Sq
- OKL - Oakville, ON
- OKO - Okemo, Vermont
- OLT - San Diego, California Old Town
- OLW - Olympia-Lacey, Washington
- OMA - Omaha, Nebraska
- OMW - Omak, Washington
- ONA - Ontario, California
- ONT - Ontario, Oregon
- ORB - Old Orchard Beach, Maine Seasonal
- ORC - Oregon City, Oregon
- ORL - Orlando, Florida
- ORO - Orono, Maine
- ORV - Oroville, California
- OSB - Old Saybrook, Connecticut - Regional
- OSC - Osceola, Iowa
- OSD - Oceanside, California
- OSH - Oshkosh, Wisconsin
- OTM - Ottumwa, Iowa
- OXN - Oxnard, California
Read more about this topic: List Of Amtrak Station Codes