A mobile or cellular telephone is a long-range, portable electronic device for personal telecommunications over long distances.

Most current mobile phones connect to a cellular network of base stations (cell sites), which is in turn interconnected to the public switched telephone network (PSTN) (the exception are satellite phones). Fully automatic cellular networks were first introduced in the early to mid 1980s (the 1G generation). The first fully automatic mobile phone system was the Nordic Mobile Telephone (NMT) system, introduced in 1981.

Prior mobile telephones (the so-called 0G generation), such as Mobile Telephone Service, date back to 1945. These were not categorized as mobile phones, since they did not support handover, i.e. automatic change of channel frequency in the middle of a call, when the user moved from one cell (base station coverage area) to another.

Until the mid to late 1980s, most mobile phones were sufficiently large that they were permanently installed in vehicles as car phones. With the advance of miniaturization, currently the vast majority of mobile phones are handheld. In addition to the standard voice function of a telephone, a mobile phone can support many additional services such as SMS for text messaging, email, packet switching for access to the Internet, and MMS for sending and receiving photos and video.

Mobile phone manufacturers include Apple Inc., Audiovox, Benefon, BenQ-Siemens, High Tech Computer Corporation, Fujitsu, Kyocera, 3G, LG, Motorola, NEC, i-mate, Nokia, Panasonic (Matsushita Electric), Pantech Curitel, Philips, Sagem, Samsung, Sanyo, Sharp, Siemens, SK Teletech, Sony Ericsson, T&A Alcatel, and Toshiba.

Mobile phone etiquette has become an important issue with mobiles ringing at funerals, weddings, cinemas, and plays. [13] Users often speak at increased volume which has led to places like book shops, libraries, movie theatres, doctors' offices, and houses of worship posting signs prohibiting the use of mobile phones, and in some places installing signal-jamming equipment to prevent usage (although in many countries, e.g., the United States, such equipment is currently illegal). Some new buildings such as auditoriums have installed wire mesh in the walls which prevents any signal getting through, but does not contravene the jamming laws.