Horse Names Beginning with o
- O Danny Boy - Oak Barrel
- Oak Door - Oasis Sunrise
- Oath Of Gold (JPN) - Ocean Crossing (NZ)
- Ocean Dash (NZ) - Octahedron (NZ)
- Octahro - Off Broadway
- Off Centre - Oh My Papa
- Oh My Rocket - Okay Pal
- Okay Swift - Olde World Charm
- Olden Times - Olympic Lad
- Olympic Legend - On Our Selection
- On Our Way (GB) - On Your Toes
- On Your Way - One in All In
- One in Five - One Track Mind
- One Tree - Only One World
- Only Orsenfoolsies (GB) - Opal Strike
- Opal Tiara (IRE) - Optic Babe
- Optic View - Orchard Street
- Orchestra - Orientaped
- Orientate (USA) - Orthie's Boy (NZ)
- Orthie's Gem - Otimo
- Otoshi - Our Blanc Canvas (NZ)
- Our Blazerboy - Our Crown Mistress
- Our Crowned Dancer - Our Gal
- Our Gal (GB) - Our Katarina
- Our Kate - Our Memory Girl
- Our Meteor - Our Principessa
- Our Private Dancer (NZ) - Our Siena
- Our Silky Smooth - Our Yangtze River
- Our Yellow Ribbons - Outback Fortune
- Outback Gambler - Ouyang Feng (NZ)
- Ouyen - Owdatay
- Owen Patrick (NZ) - Ozzie's Touch
Horse Directory: O Danny Boy - Oak Barrel
- O Danny Boy
- O O Seven (IRE)
- O Ren Ishii
- O Sole Mio
- O' Aphrodite
- O' Monty Zuma
- O' So
- O' So Handy
- O' So Hazy
- O' Susie
- O' Venus
- O' What a Rush (NZ)
- O'angel (NZ)
- O'behave
- O'bella Bai
- O'brien
- O'bro
- O'callagan
- O'canny (NZ)
- O'carol (NZ)
- O'Carol (NZ)
- O'cartier (NZ)
- O'ceirins Angel (NZ)
- O'ceirins Choice (NZ)
- O'ceirins Pal (NZ)
- O'ceirins Secret (NZ)
- O'Charm (NZ)
- O'connell
- O'Connor
- O'connor (NZ)
- O'couney (NZ)
- O'Crikey (NZ)
- O'dahlia (NZ)
- O'darci (NZ)
- O'darl
- O'dehere Me
- O'dellini
- O'dianne (NZ)
- O'donoghues Ruler
- O'dorcia (NZ)
- O'driscoll (NZ)
- O'erin
- O'faberge (NZ)
- O'fame
- O'feelya (NZ)
- O'Fennessy
- O'fille (NZ)
- O'filliate (NZ)
- O'flirty
- O'for the Moment
- O'fortuna
- O'Gio
- O'giselle
- O'gosh
- O'grace
- O'grady (NZ)
- O'guy (NZ)
- O'Guy (NZ)
- O'hara (NZ)
- O'hara (NZ)
- O'hara de Belle
- O'hare
- O'he Can (NZ)
- O'hearne
- O'heck (NZ)
- O'jay
- O'jessie
- O'junior
- O'just Saying (NZ)
- O'katie
- O'keefe
- O'kiwi (NZ)
- O'know (NZ)
- O'komon
- O'Lino
- O'lonera
- O'lonh Star
- O'lonhro
- O'lonhro Bay
- O'lonhroad
- O'lonrose Way
- O'lordy
- O'loughlin
- O'lovely (NZ)
- O'lynch
- O'malley
- O'marie
- O'marilyn
- O'marilyn
- O'marnie
- O'mimic
- O'mizzna
- O'mudgee (NZ)
- O'naturelle (NZ)
- O'Naturelle (NZ)
- O'nestal
- O'niello
- O'nory
- O'perfect One
- O'princess (NZ)
- O'princess (NZ)
- O'rachael
- O'rachael
- O'raghailligh (NZ)
- O'rana Belle
- O'rayo (NZ)
- O'Really
- O'Reilly (NZ)
- O'reilly Cyrus (NZ)
- O'reilly Express (NZ)
- O'reilly Factor
- O'Reilly Magic (NZ)
- O'reilly Rally (NZ)
- O'reilly Rose (NZ)
- O'reilly's Angel (NZ)
- O'reilly's Charm (NZ)
- O'reilly's Choice (NZ)
- O'reilly's Clock (NZ)
- O'reilly's Crumpet (NZ)
- O'reilly's Dancer (NZ)
- O'Reilly'S Dancer (NZ)
- O'reilly's Gold (NZ)
- O'reilly's Prize (NZ)
- O'reilly's Prize (NZ)
- O'reilly's Revenge (NZ)
- O'reilly's Son (NZ)
- O'reillys Geegee (NZ)
- O'resonate (NZ)
- O'sasha (NZ)
- O'so Tempting
- O'solexi
- O'spacehello
- O'susie's Boy
- O'tauto
- O'thunder
- O'tobefamous (NZ)
- O'tonda
- O'toole
- O'torio
- O'touche
- O'tryst (NZ)
- O'vaticano
- O'well
- O'witchway
- Oahu Ace
- Oahu Gem
- Oahu Girl
- Oahu Sunset
- Oak 'n' Arthur
- Oak Barrel
