| Our Market Research Shows That Players Like Really Long Card Names So We Made this Card to Have the Absolute Longest Card Name Ever ElementalUnhinged · 107 | Unhinged | 107 | Common | €0.35 |
| Out ColdMurders at Karlov Manor · 66 | Murders at Karlov Manor | 66 | Common | €0.11 |
| OutflankThrone of Eldraine · 23 | Throne of Eldraine | 23 | Common | €0.07 |
| OutflankFoundations Jumpstart · 233 | Foundations Jumpstart | 233 | Common | €0.24 |
| Outlaw MedicOutlaws of Thunder Junction · 23 | Outlaws of Thunder Junction | 23 | Common | €0.10 |
| Outlaws' FuryOutlaws of Thunder Junction · 136 | Outlaws of Thunder Junction | 136 | Common | €0.07 |
| OutmuscleThrone of Eldraine · 170 | Throne of Eldraine | 170 | Common | €0.08 |
| OutmuscleThe List Tokens · ELD-170 | The List Tokens | ELD-170 | Common | €0.05 |
| OutnumberBattle for Zendikar · 150 | Battle for Zendikar | 150 | Common | $0.11 |
| OutnumberJumpstart · 354 | Jumpstart | 354 | Common | €0.15 |
| OutnumberJumpstart 2022 · 578 | Jumpstart 2022 | 578 | Common | €0.21 |
| OutnumberThe List Tokens · BFZ-150 | The List Tokens | BFZ-150 | Common | €0.09 |
| Out of AirThe Lost Caverns of Ixalan · 69 | The Lost Caverns of Ixalan | 69 | Common | €0.12 |
| Outrider of JhessShards of Alara · 52 | Shards of Alara | 52 | Common | €0.05 |
| OutwitAvacyn Restored · 70 | Avacyn Restored | 70 | Common | $0.06 |
| Overeager ApprenticeDuel Decks: Divine vs. Demonic · 35 | Duel Decks: Divine vs. Demonic | 35 | Common | $0.20 |
| Overeager ApprenticeDuel Decks Anthology: Divine vs. Demonic · 35 | Duel Decks Anthology: Divine vs. Demonic | 35 | Common | $0.36 |
| Overeager ApprenticeOdyssey · 154 | Odyssey | 154 | Common | $0.21 |
| Overgrown ArmasaurRivals of Ixalan · 141 | Rivals of Ixalan | 141 | Common | €0.11 |
| Overgrown ArmasaurThe List Tokens · RIX-141 | The List Tokens | RIX-141 | Common | €0.19 |
| Overgrown BattlementRise of the Eldrazi · 203 | Rise of the Eldrazi | 203 | Common | $0.37 |
| Overgrown PestMarch of the Machine · 197 | March of the Machine | 197 | Common | €0.03 |
| OvergrowthTenth Edition · 283 | Tenth Edition | 283 | Common | €0.24 |
| OvergrowthTenth Edition · 283★ | Tenth Edition | 283★ | Common | €0.22 |
| OvergrowthWarhammer 40,000 Commander · 219 | Warhammer 40,000 Commander | 219 | Common | €0.39 |
| OvergrowthWarhammer 40,000 Commander · 219★ | Warhammer 40,000 Commander | 219★ | Common | $2.47 |
| OvergrowthNinth Edition · 262 | Ninth Edition | 262 | Common | €0.19 |
| OvergrowthNinth Edition · 262★ | Ninth Edition | 262★ | Common | $0.38 |
| OvergrowthCommander 2018 · 157 | Commander 2018 | 157 | Common | €0.05 |
| OvergrowthJumpstart 2022 · 702 | Jumpstart 2022 | 702 | Common | €0.28 |
| OvergrowthStronghold · 111 | Stronghold | 111 | Common | €0.37 |
| OvergrowthThe List Tokens · 9ED-262 | The List Tokens | 9ED-262 | Common | $0.25 |
| OverloadInvasion · 157 | Invasion | 157 | Common | $0.75 |
| OverrideMirrodin · 45 | Mirrodin | 45 | Common | €0.05 |
| OverruleDuel Decks: Venser vs. Koth · 32 | Duel Decks: Venser vs. Koth | 32 | Common | €0.09 |
| OverruleDissension · 120 | Dissension | 120 | Common | €0.03 |
| Over the EdgeThe Lost Caverns of Ixalan · 205 | The Lost Caverns of Ixalan | 205 | Common | €0.11 |
| Overwhelming RemorseThe Brothers' War · 110 | The Brothers' War | 110 | Common | $0.16 |
| Overzealous MuscleOutlaws of Thunder Junction · 97 | Outlaws of Thunder Junction | 97 | Common | €0.05 |
| OvinizeDominaria Remastered · 63 | Dominaria Remastered | 63 | Common | $0.08 |
| OvinizeDominaria Remastered · 291 | Dominaria Remastered | 291 | Common | $0.08 |
| OwlbearAdventures in the Forgotten Realms · 198 | Adventures in the Forgotten Realms | 198 | Common | €0.11 |
| OwlbearAdventures in the Forgotten Realms · 331 | Adventures in the Forgotten Realms | 331 | Common | €0.10 |
| OwlbearAlchemy Horizons: Baldur's Gate · 218 | Alchemy Horizons: Baldur's Gate | 218 | Common | — |
| Owl FamiliarRavnica: Clue Edition · 90 | Ravnica: Clue Edition | 90 | Common | $0.16 |
| Owl FamiliarFoundations Jumpstart · 342 | Foundations Jumpstart | 342 | Common | €0.16 |
| Owl FamiliarPortal · 63 | Portal | 63 | Common | $0.40 |
| Owl FamiliarThe List Tokens · POR-63 | The List Tokens | POR-63 | Common | €0.08 |
| Owl FamiliarMasters Edition IV · 54 | Masters Edition IV | 54 | Common | — |
| Owl FamiliarVintage Masters · 85 | Vintage Masters | 85 | Common | — |