ZyXEL Communications Corp. (Chinese:合勤科技, Holding company Unizyx TSE: 3704), located in Hsinchu, Taiwan, is a manufacturer of DSL and other networking devices. (Gartner, August 2005). With headquarters in Taiwan, ZyXEL maintains branch offices in North America, Europe, and Asia. Currently, ZyXEL has around 2100 employees globally, with distributors in more than seventy countries, and products marketed in more than 150 countries on five continents. ZyXEL works with worldwide network equipment vendors, telecommunications companies, ISPs, and other small to medium businesses.

ZyXEL commonly acts as OEM for ISPs or system integrators. It is common for a DSL user to get an ISP-branded DSL modem from their ISP; for example Earthlink issues ZyXEL ADSL modems that have the suffix "-ELINK" at the end of the model number, and the configuration screens contain the Earthlink logo. Branding the setup screens with the ISP's corporate identity is accompanied with the ability to specify default configuration settings appropriate for their network, thus simplifying the setup directions they ship to a new customer.