A Satellite Phone or Sat Phone is a type of mobile phone that connects to other phones or the telephone network by radio link through satellites orbiting the Earth instead of terrestrial cell sites, as cell phones do. Therefore, they can work in most geographic locations on the Earth’s surface, as long as open sky and the line-of-sight between the phone and the satellite are provided. Depending on the architecture of a particular system, coverage may include the entire Earth or only specific regions.

Satellite phones provide similar functionality to terrestrial mobile telephones; voice calling, text messaging, and low-bandwidth Internet access are supported through most systems. The advantage of a sat phone is that it can be used in such regions where local terrestrial communication infrastructures, such as landline and cellular networks, are not available.