3G refers to the third generation of developments in wireless technology, especially mobile communications. The third generation, as its name suggests, follows the first generation (1G) and second generation (2G) in wireless communications.

1G - The 1G period began in the late 1970s and lasted through the 1980s. These systems featured the first true mobile phone systems, known at first as "cellular mobile radio telephone." These networks used analog voice signaling, and were little more sophisticated than the repeater networks used by amateur radio operators.

2G - The 2G phase began in the 1990s and much of this technology is still in use. The 2G cell phone features digital voice encoding. Examples include CDMA and GSM. Since its inception, 2G technology has steadily improved, with increased bandwidth, packet routing, and the introduction of multimedia.

3G includes capabilities and features such as:
Enhanced multimedia (voice, data, video, and remote control).
Usability on all popular modes (cellular telephone, e-mail, paging, fax, videoconferencing, and Web browsing).

Broad bandwidth and high speed (upwards of 2 Mbps).
Roaming capability throughout Europe, Japan, and North America.
While 3G is generally considered applicable mainly to mobile wireless, it is also relevant to fixed wireless and portable wireless.

A 3G system should be operational from any location on, or over, the earth's surface, including use in homes, businesses, government offices, medical establishments, the military, personal and commercial land vehicles, private and commercial watercraft and marine craft, private and commercial aircraft (except where passenger use restrictions apply), portable (pedestrians, hikers, cyclists, campers), and space stations and spacecraft.
3G offers the potential to keep people connected at all times and in all places. Researchers, engineers, and marketers are faced with the challenge of accurately predicting how much technology consumers will actually be willing to pay for.

Another challenge faced by 3G services is competition from other high-speed wireless technologies, especially mobile WiMAX, and ability to roam between different kinds of wireless networks.

The current status of mobile wireless communications, as of July 2007, is a mix of 2nd and 3rd generation technologies.