XO Communications
| XO | |
| Company type | Subsidiary | 
| Industry | Telecommunications | 
| Predecessors | 
 | 
| Founded | July 4, 1996 in Bellevue, Washington | 
| Fate | Replaced by Verizon | 
| Successor | Verizon Communications | 
| Headquarters | , | 
| Areas served | Primarily the United States, South America, Europe, Middle East, Asia and Oceania | 
| Key people | |
| Products | VoIP services, Network Services, Hosted Services, Carrier / Wholesale | 
| Website | www | 
XO Communications, LLC, previously Nextlink Communications, Concentric Network Corporation and Allegiance Telecom, Inc., was an American telecommunications company. It was purchased and replaced by Verizon Communications.