| XeroAccounting Software & Online Bookkeeping | Xero | Computer Software | London | England | > $1B |
| | Financial Services | San Francisco | CA | $50 - 100M |
| xMatters, incBest IT Notification software to power IT Operations - xMatters Inc | Computer Software | San Ramon | CA | $10 - 50M |
| XirrusHigh Performance Enterprise Grade Wi-Fi Solutions / Access Points | Wireless | Thousand Oaks | CA | $50 - 100M |
| X1X1 | Knowledge revealed | Computer Software | Pasadena | CA | $1 - 10M |
| XplentyData Integration Service. Simplified. · Xplenty | Information Services | Tel Aviv | CA | $1 - 10M |
| XMPieMultichannel and VDP Marketing Software | XMPie | Computer Software | New York | NY | $10 - 50M |
| | Telecommunications | Wakefield | MA | |
| X-FormationSoftware License Management & more | X-Formation | Computer & Network Security | Tilst | | |
| | Information Technology and Services | Vancouver | BC | $1 - 10M |
| XenetaXeneta Home - Are you paying the right ocean freight rates? | Internet | Oslo | | $1 - 10M |
| XPLANEGet Aligned | XPLANE | Visual Thinking | Strategy Execution | Management Consulting | Portland | OR | $1 - 10M |
| XOJETXOJET | The Leader in On-Demand Private Jet Charter & Luxury Travel | Airlines/Aviation | San Carlos | CA | $100 - 250M |
| XeikonDigital printing solutions for printing business | Xeikon | Printing | Eede | | $1 - 10M |
| | Information Technology and Services | Leatherhead | Surrey | |
| | Computer Software | Simi Valley | CA | $1 - 10M |
| | Broadcast Media | Langhorne | PA | |
| | Management Consulting | SAN FRANCISCO | CA | $0 - 1M |
| | Hospital & Health Care | Newtown Square | PA | $100 - 250M |
| XactiumRisk Management Solutions | Xactium | Farming | Sheffield | | |
| X-onX-on Cloud Communications | Telecommunications | Framlingham | Suffolk | |
| XtanditXtandit - Business partner voor documentprocessen & printomgevingen | Business Supplies and Equipment | Woerden | Utrecht | |
| | Internet | Heidelberg | | |
| X15 SoftwareLarge-Scale Machine and Log Data Management | X15 Software, Inc. | Computer Software | | | |
| | Information Technology and Services | MCLEAN | VA | $1 - 10M |
| Xcelerated, Inc.Vehicle & Data Services - Enhance Your Marketing with Xcelerated, Inc. | Information Services | Hebron | KY | $1 - 10M |
| | Computer Software | Mountain View | CA | $0 - 1M |
| | Information Technology and Services | Lima | | |
| | Financial Services | London | | |
| | Computer Software | | | $1 - 10M |
| | Information Technology and Services | | | |
| | Marketing and Advertising | Tel Aviv | | $0 - 1M |
| | Information Technology and Services | | | $0 - 1M |
| | Information Technology and Services | Mississauga | ON | |
| | Computer & Network Security | Las Vegas | NV | $1 - 10M |