| Datagram Informatica Soc. Coop | Milan |
| Datalab S.r.l. | Padua |
| DataLabor.com | Parma |
| Datalogic | Bologna |
| Datamatic S.p.A. | Milan |
| DataMind S.r.l. | |
| Datarecovery S.r.l. | Rome |
| DataSecurity S.r.l.s. | Friuli-Venezia Giulia |
| DataSoftware S.r.l. | Bari |
| Datasys Network S.r.l. | Milan |
| Datatex | Milan |
| Dataweb Service | Milan |
| Datawizard | Rome |
| Dataworks S.a.s. | Rome |
| Date Group S.r.l. | Turin |
| Datef AG | South Tyrol |
| Dati.gov.it | Rome |
| DatoCMS | Florence |
| Davide Nanni Web Agency Bologna | Bologna |
| Davidedattoli | Brescia |
| DaVinciFace AI | Florence |
| Day One | Rome |
| DazeTechnology S.r.l. | |
| DB Elettronica Telecomunicazioni S.p.A. | Padua |
| DBridge | Milan |
| De' Sign S.C. | Venice |
| DEA Security S.r.l. | La Spezia |
| Dea System S.r.l. | Vicenza |
| Debba.it | Genoa |
| Deca S.r.l. | Turin |
| Decodo | Bergamo |
| Deda Group | Trento |
| Dedalo AI S.r.l. | |
| Dedalus Global S.p.A. | |
| Deep Oean Capital SGR S.p.A. | |
| Deicon S.r.l. | Milan |
| Delcaldo | Pisa |
| Deliverart S.r.l. | |
| Deliveristo S.p.A. | |
| Deliveristo S.p.A. | |
| Delos S.r.l. | |
| Delphinet | Rome |
| Delta i S.r.l. | Massa-Carrara |
| Delta Ohm S.r.l. | Padua |
| Delta System S.p.A. | Treviso |
| Delta x Multimedia | Barletta-Andria-Trani |
| Demal Elettronica S.r.l. | Forlì-Cesena |
| Demetrio Polimeno | Bologna |
| DemiSolutions | Rimini |
| DensityDesign | |