| Oran-Rief Invoker | DDR-17 |
| Oracle of Nectars | SHM-233 |
| Opulent Palace | KTK-238 |
| Opulent Palace | OTC-307 |
| Opt | DOM-60 |
| Oppression | USG-143 |
| Opportunity | ULG-37 |
| Opportunity | C17-89 |
| Ophidian Eye | TSP-70 |
| Ophidian | WTH-45 |
| Opal Lake Gatekeepers | DGM-16 |
| Onslaught | EXO-92 |
| Oneirophage | MH1-60 |
| One with Nothing | SOK-84 |
| One with Nature | SCG-125 |
| Ondu War Cleric | OGW-31 |
| Ondu Inversion // Ondu Skyruins | ZNR-30 |
| Ondu Greathorn | BFZ-40 |
| Ondu Giant | PCA-71 |
| Ondu Champion | BFZ-149 |
| Once Upon a Time | ELD-169 |
| Onakke Ogre | M19-153 |
| On Serra's Wings | DOM-28 |
| Omnath, Locus of Rage | BFZ-217 |
| Ominous Seas | IKO-61 |
| Omenspeaker | BBD-125 |
| Omen of the Sun | THB-30 |
| Omen of the Sea | THB-58 |
| Omen | POR-62 |
| Oloro, Ageless Ascetic | C13-203 |
| Olivia's Bloodsworn | SOI-127 |
| Olivia, Mobilized for War | SOI-248 |
| Old Gnawbone | AFR-197 |
| Old Ghastbark | SHM-232 |
| Oko, the Trickster | ELD-309 |
| Okina, Temple to the Grandfathers | CHK-280 |
| Okiba-Gang Shinobi | PCA-35 |
| Oketra's Monument | AKH-233 |
| Ojutai's Breath | DTK-67 |
| Ojutai Interceptor | DTK-66 |
| Ohran Frostfang | C19-33 |
| Ogre Gatecrasher | DIS-67 |
| Ogre Arsonist | P02-110 |
| Odric, Master Tactician | M13-23 |
| Odric, Lunarch Marshal | SOI-31 |
| Odric, Lunarch Marshal | DMC-103 |
| Odds // Ends | DIS-153 |
| Octopus Umbra | C18-11 |
| Ochran Assassin | GRN-194 |
| Obsessive Stitcher | M21-223 |