Region | Title | System | Version | Edition | Languages | Serial | Status |
| Oto to E no Deru Eigo Jisho No. 1: Start with Words 音と絵の出る英語辞書 No.1 「Start with Words」 | FMT | | Original, Rerelease | | HMA-217 | |
| Oto to E no Deru Eigo Jisho No. 2: English in Dream 音と絵の出る英語辞書 No.2 「English in Dream」 | FMT | | Original | | HMB-129 | |
| Oto to E no Deru Eigo Jisho No. 4: Nandemo Illust Eigo Jiten Part 2 音と絵の出る英語辞書 No.4 「なんでもいらすとえいごじてん Part 2」 | FMT | | Original | | HMB-170 | |
| Obsidian (Disc 1) | MAC | | Original, Great Series | | INR-001, MKM-001 | |
| Obsidian (Disc 2) | MAC | | Original, Great Series | | INR-001, MKM-001 | |
| Obsidian (Disc 3) | MAC | | Original, Great Series | | INR-001, MKM-001 | |
| Obsidian (Disc 4) | MAC | | Original, Great Series | | INR-001, MKM-001 | |
| Obsidian (Disc 5) | MAC | | Original, Great Series | | INR-001, MKM-001 | |
| Oceans Below オーシャンズ・ビロウ | MAC | | Original | | MSC001 | |
| Oceans Below The Software Toolworks Presents ... Oceans Below | MAC | | Original | | 2198620-590001 / I 073100, CDRM1103420 | |
| Oddworld: Abe's Exoddus: UK Packaging | MAC | | Art Assets | | | |
| Oddworld: Abe's Exoddus: US Manual | MAC | | Art Assets | | | |
| Obduction | MAC | | Kickstarter | | | |
| Omgaan met Steriele Medische Hulpmiddelen | CDI | | Demo | | | |
| Omgaan met Steriele Medische Hulpmiddelen Omgaan met Steriele Medische Hulp-Middelen | CDI | | Original | | | |
| One Step Ahead | CDI | | | | Demo 10.05.94 | |
| Ontdek de Interactieve Wereld van Neckermann | CDI | | Original | | | |
| Op Jacht naar Vernuft | CDI | | | | | |
| L'Open de Palm Springs | CDI | | Original, For Demonstration Only | | 812 0002 | |
| Open Universiteit: Practicum Toxicologische Histopathologie Open University: Practical Toxicological Histopathology | CDI | | Original | | 4589 | |
| OptImage CD-I 220 Adjustment Disc | CDI | | Original | | | |
| OptImage CD-I Starter System: Sampler Disc: Version 1.1 | CDI | | | | | |
| Origami | CDI | | Original | | 810 0041 | |
| De Overval: Over Dwangmiddelen en Getuigenverhoor | CDI | | Original | | ovrvl 01 | |
| Oldtimer | PHOTO-CD | | Original | | 813 0067 | |
| Opel Corsa '97 | PHOTO-CD | | Original | | | |
| Opel IAA '97 | PHOTO-CD | | Original | | | |
| Opel IAA '99 (Disc 1) (Model Range) | PHOTO-CD | | Original | | | |
| Opel IAA '99 (Disc 2) (Opel Highlights) | PHOTO-CD | | Original | | | |
| Opel Vectra '99 | PHOTO-CD | | Original | | | |
| Osaka City 大阪 | PHOTO-CD | | Original | | | |
| Ozaki Yutaka: Eyes: "Hakushi no Sanran" Yori 尾崎 豊 eyes「白紙の散乱」より | PHOTO-CD | | | | CAT.908753-7 | |
| ODN Palm Power Pack | PALM | | Original | | | |
| Oh-chan no Oekaki Logic for Palm おーちゃんのお絵かきロジック for Palm | PALM | 1.04 | Original | | | |
| OnHand Chess / Sega Swirl Lite | PALM | PDA103-01 | Original | | PDA103-01 | |
| OnHand Complete Astrologer OnHand Complete Astrologer: Horoscopes & More! | PALM | PDA108-01 | OnHand Double Pack (Sports Games/Astrologer) | | PDA108-01 | |
| OnHand Sports Games / Sega Swirl Lite | PALM | PDA105-01 | OnHand Double Pack (Sports Games/Astrologer) | | PDA105-01 | |
| Oxford Handbook of Clinical Medicine for PDAs: Seventh Edition | PALM | 10.0.05/2007.9.7 | | | | |
| Oh!X 1998 Spring Special CD-ROM (Part 2) (Sampler Disc) | X68K | | | | | |
| Oh!X 1998 Spring Special CD-ROM (Part 1) | X68K | | | | | |
| Oh!X 1999 Spring Special CD-ROM (Part 2) (Sampler Disc) | X68K | | | | | |
| Oh!X 1999 Spring Special CD-ROM (Part 1) | X68K | | | | | |
| Oh!X 1999 Summer Special CD-ROM | X68K | | | | | |
| Oh!X 2000 Spring Special CD-ROM (Part 1) | X68K | | | | | |
| Oh!X 2000 Spring Special CD-ROM (Part 2) | X68K | | | | | |
| Oh!X 2001 Spring Special CD-ROM | X68K | | | | | |
| One-derful Theater ONEだふるシアター | X68K | | | | | |
| Oregano Oregano: RISC OS Web Browser | ARCH | | Original | | | |
| Ovation | ARCH | 1.48S | | | 00139 | |
| Oha Suta Series 01: Zonapara おはスタシリーズ01 象南波羅~ゾナパラ~ | KSITE | | Original | | 536956 | |
| Oha Suta Series 02: Oha Ska! おはスタシリーズ02 おは スカ | KSITE | | Original | | 538714 | |
| Our House featuring The Family Circus | VIS | | Original | | 25-6146 | |
| Otomedius (System Disc) オトメディウス | KEA | JAA | Original | | GGGJAA01 | |
| Otomedius (Application Disc 2) オトメディウス | KEA | JAA | Original | | GGGJAA03 | |
| Otomedius (Application Disc 1) オトメディウス | KEA | JAA | Original | | GGGJAA02 | |
| Ollie King オーリーキング | CHIHIRO | 1.003 | Original | | GDX-0007 | |
| OutRun 2 | CHIHIRO | 2.000 | Original | | GDX-0004A | |