| Lastname | Firstname | Casefile | Photos | Type of Abuse | Case Status | Other Crimes | State | City/Town | Province | Country | Date | Next Court Date | Last known address |
| Oberkirsch | Janis | Woman pleads guilty to animal cruelty | Hoarding | Convicted | TN | La Vergne | USA | 02/2004 | |||||
| Ochoa | Salvador | Cockfighting, gambling, drugs and weapons seized | Fighting | Alleged | child endangerment | CA | San Bernardino | USA | 01/23/99 | ||||
| O'Donnell | Chris | Horse and dog neglect | Neglect/Abandonment | Convicted | NJ | Vineland | USA | 08/22/2003 | |||||
| O'Donnell | Ursula | Greyhound Killings | Neglect/Abandonment | Alleged | AL | Baldwin County | USA | 06/30/2004 | |||||
| Ogletree | Kennedy Wayne | Cruelty to 23 pit bull dogs | yes | Neglect/Abandonment | Alleged | GA | Mableton | USA | 01/04/2000 | ||||
| Oh | Jeong | Terrier dragged behind car | Vehicular Torture | Convicted | VA | Great Falls | USA | 06/28/2003 | |||||
| Ojeda | Paul | Hoarding | Hoarding | Convicted | CA | San Diego | USA | 01/31/2003 | |||||
| Olan | Joseph | Neglect (dog) | Neglect | Convicted | London | Ontario | Canada | 02/14/2001 | |||||
| Olan | Joseph | Violating "no possession" court order | Neglect/Abandonment | Convicted | London | Ontario | Canada | 02/29/2000 | |||||
| Oliver | Issac | Strangling a cat, attempting to kill another | Torture | Convicted | NY | Albany | USA | 12/1/2003 | |||||
| Olsen | James L. | Dog Fighting/animal cruelty | Fighting | Alleged | NM | Carslbad | USA | 11/16/2001 | |||||
| Olson | Darcy Lee | Bit throat out of live rabbit | Mutilation/Torture | Convicted | OR | Multnomah County | USA | 09/2001 | |||||
| Olson | Ronda | Neglect of 5 horses | Neglect/Abandonment | Alleged | IN | Jackson Township | USA | 07/06/1991 | |||||
| Oman, Jr. | Earl | Trapped cat and set on fire | Burning | Alleged | PA | Briar Creek Township | USA | 11/26/2001 | |||||
| Ommart | Mark Edward | Stabbing a 6-month-old horse | Mutilation/Torture | Convicted | IN | Crown Point | USA | 11/10/1991 | |||||
| O'Neal | Joseph Ray | Stabbed girlfriends dog, killed mother and stepfather | Yes | Torture | Alleged | domestic abuse, murder | OR | Portland | USA | 4/2/2006 | |||
| O'Neil | Robert S. | Pitbull beaten with sledgehammer | Torture | Alleged | IL | Naperville | USA | 6/3/2006 | |||||
| O'Neill | Susan Marie | Horse went without veterinary care for 22 years | Neglect | Convicted | FL | Middleburg | USA | 8/4/2006 | |||||
| Onunwah | Godwin Collins | Teacher suffocated rabbit in special ed class | Mutilation/Torture | Acquitted | CA | Los Angeles | USA | 12/31/2000 | |||||
| Ornelas | Jesse | cockfighting | Fighting | Alleged | CA | San Jose | USA | 07/17/99 | |||||
| Orszulak | Darlene | Kennel operator faces 61 animal cruelty | Neglect/Abandonment | Alleged | PA | Latrobe | USA | 03/23/2004 | |||||
| Ort | Sarah | Woman Starves Dogs to Death | Neglect/Abandonment | Alleged | PA | State College | USA | 07/25/2004 | |||||
| Ortega | Enrique | Cockfighting - 41 birds seized | Fighting | Alleged | GA | Tifton | USA | 4/16/2006 | |||||
| Ortiz | Aram | Puppy beaten for urinating, plunged off 5-story roof - dies | Torture | Alleged | NY | New York | USA | 4/16/2006 | |||||
| Ortiz | Poliocarpo | Possession of cockfighting birds | Fighting | Convicted | CA | San Diego | USA | 08/05/2002 | |||||
| Ortiz | Poliocarpo | Possession of cockfighting paraphernalia | Fighting | Convicted | CA | San Diego | USA | 01/2003 | |||||
| Osborne | Chris | Horse neglect | Neglect/Abandonment | Alleged | OH | Springboro | USA | 11/2003 | |||||
| Osborne | Sherrie | Horse neglect | Neglect/Abandonment | Alleged | OH | Springboro | USA | 11/2003 | |||||
| Oshodin | Osahon | Hacked dog to death with machete | Mutilation/Torture | Alleged | OH | Toledo | USA | 07/30/2002 | |||||
| Oshodin | Osaigbovo | Hacked dog to death with machete | Mutilation/Torture | Alleged | OH | Toledo | USA | 07/30/2002 | |||||
| Osorio | Francisco | Cockfighting - 18 birds | Fighting | Alleged | FL | Naples | USA | 07/24/2003 | |||||
| Otto | Gary | Sex with cattle | Beastiality | Open | WI | Menomonie | USA | 07/08/2001 | |||||
| Otto | Heidi | Neglect of 13 horses | Neglect/Abandonment | Convicted | NY | Lithgow | USA | 03/12/2003 | |||||
| Overbey | Gary Don | Chopped dog's head off with axe | Mutilation/Torture | Alleged | OK | Oklahoma City | USA | 05/26/2003 | |||||
| Owens | Bradley D. | Allowing pit bulldogs to repeatly attack | Fighting | Alleged | GA | Tifton | USA | 02/03/2004 | |||||
| Owens | Dexter Montana | Dog-fighting 123 people arrested | Fighting | Alleged | GA | Covington | USA | 01/19/2004 | |||||
| Owens | Johnny Christopher | Dog sexually | Beastiality | Alleged | CA | Lucerne Valley | USA | 3/13/2006 | |||||
| Owens | Walter | Horse neglect - 8 horses seized | Neglect/Abandonment | Alleged | AR | Texarkana | USA | 05/2002 | |||||
| Ozcan | Tuncay | Sexually assaulting horse | Beastiality | Convicted | Southampton | England | England | 07/15/2003 | |||||
| Oziomek | Michael | Shaved, wrote on, and beat cat | Torture | Alleged | CT | New Britain | USA | 02/16/2002 | |||||