| NurjanaTech | Cagliari |
| NUWA Technologies S.r.l. | |
| NWG S.p.A. | Prato |
| NyE Consulting | Parma |
| NYP Techfin | Rome |
| O-One S.r.l. | Milan |
| O.C.R. System | Turin |
| Objectway | Milan |
| Objectway | Milan |
| OBLIQUID S.r.l. | Bergamo |
| OBS S.r.l. | Mantua |
| Oddi S.a.s. | Milan |
| Oem Automazione | Milan |
| Office Trade S.p.A. | Modena |
| OfficeJam | Rome |
| Officina Creativa | Brescia |
| Officine Informatiche S.r.l. | Frosinone |
| Officine Pixel | Forlì-Cesena |
| Ohoskin | |
| OKRIM S.n.c. | Vicenza |
| OLFA Technologies | Turin |
| Olivetti S.p.A. | Turin |
| Olon S.p.A. | |
| Oltre Impact SGR S.p.A. | |
| Oltremare S.r.l. | Lodi |
| Omedra S.r.l. | Trento |
| Omicron Consulting S.r.l. | Turin |
| Omikron Italia S.r.l. | |
| Omitech | Padua |
| Omnia Studio S.a.s. | Rome |
| Omnicon S.r.l. | Monza and Brianza |
| Omnidea S.r.l. | Venice |
| Omniink | Bari |
| Omnisoft S.r.l. | Milan |
| Omnys S.r.l. | Vicenza |
| Onangel S.r.l.s. | Lecce |
| Ondenet | Rimini |
| One On Line | Salerno |
| Onebip S.p.A. | Milan |
| Onedirect | Milan |
| OneTray S.p.A. | |
| OnLine Common Sense | Caserta |
| Onyon S.r.l. | |
| OPByte Software | Rome |
| Open Accelerator | Milan |
| Open Data S.r.l. | Bologna |
| Open IT S.r.l. | Trento |
| Open Lab S.r.l. | Florence |
| Open Observatory of Network Interference | |
| Open S.a.s. | Padua |