| Osaka Seikei Gakuen | |
| Osaka Sekei University | |
| Osaka Shin-Ai Jogakuin | |
| Osaka Tokiwakai University | |
| Osaka University | Osaka |
| Osaka University - Department of Mathematics | Osaka |
| Osaka University of Arts | |
| Osaka University of Commerce | |
| Osaka University of Economics | |
| Osaka University of Economics and Law | |
| Osaka University of Health and Sport Sciences | |
| Osaka University of Human Sciences | |
| Osaka University of Tourism | |
| OSAKA University Venture Capital Co., Ltd | |
| OSG-SYS | Ehime |
| OsidOri, Inc. | |
| OSSTech Corporation | Tokyo |
| Otani University | |
| Otaru University of Commerce | |
| Otemae Educational Corporation | |
| Otemon Gakuin University | |
| OTK Co., Ltd | Tokyo |
| Otsuka Corporation | Tokyo |
| Otsuma Women's University | Tokyo |
| Otsumu Co., Ltd | Tokyo |
| oVice, Inc. | |
| Owari Gakuen | |
| OyaTech | |
| Ozvision Co., Ltd | Tokyo |
| P Softhouse Co., Ltd | Miyagi |
| P.R.A. Co., Ltd | Chiba |
| Paidy | Tokyo |
| Paidy.com | Tokyo |
| PALTEK Corporation | Tokyo |
| Paltiosoft, Inc. | Tokyo |
| Panasonic Holdings Corporation | Osaka |
| Pandanet, Inc. | Tokyo |
| Parallel, Inc. | |
| Parasite.com | Kyoto |
| Partners Fund | |
| Pasco Corporation | Tokyo |
| Pasocomclub Co., Ltd | Tokyo |
| Pasolet | Tokyo |
| Pasona Tech, Inc. | Tokyo |
| Passoclub Co., Ltd | Shiga |
| Payme Co., Ltd | Tokyo |
| Payment Technology Co., Ltd | Tokyo |
| PayPay Corporation | Tokyo |
| PC DEPOT Corporation | Tokyo |
| PC Doskoi | Tokyo |