3G is third-generation technology in the context of mobile phone standards. The services associated with 3G include wide-area wireless voice telephony, and broadband wireless data, all in a mobile environment. In marketing 3G services, video telephone has often been suggested as the killer application for 3G.

According to the GSA, in December 2005 there were 100 3G networks in operation in 40 countries in the world. In Asia, Europe, and the USA, telecommunication companies use W-CDMA technology with the support of around 100 terminal designs to operate 3G mobile networks.

Roll-out of 3G networks was delayed in some countries by the enormous costs of additional spectrum licensing fees. In many parts of the world 3G networks do not use the same radio frequencies as 2G, requiring mobile operators to build entirely new networks and license entirely new frequencies; a notable exception is the United States where carriers operate 3G service in the same frequencies as other services. The license fees in some European countries were particularly high, bolstered by initial excitement over 3G’s potential. Other delays were as a result of the expenses related to upgrading equipment for the new systems.

The first country that introduced 3G on a large commercial scale was Japan. In 2005, about 40% of subscribers used 3G networks only, with 2G being on the way out. It was expected that the transition from 2G to 3G would be largely completed during 2006, and upgrades to the next 3.5G stage with 3 Mbit/s data rates were under way.

The successful 3G introduction in Japan showed that video telephony was not the killer application for 3G networks after all. The real-life usage of video telephony on 3G networks was found to be a small fraction of all services. On the other hand, downloading of music found strong acceptance by customers. Music download services in Japan were pioneered by KDDI with the EZchakuuta and Chaku Uta Full services.

3G networks are not IEEE 802.11 networks. IEEE 802.11 networks are short range, higher-bandwidth (primarily) data networks, while 3G networks are wide area cellular telephone networks which evolved to incorporate high-speed internet access and video telephony.