(SOFTware PHONE) A software-based phone for voice over IP (VoIP) that is installed in the user's PC. The audio interface can be a microphone and speakers plugged into the sound card, although a headset is preferred. For better clarity, a USB phone or Bluetooth phone can be used.

Softphones can work as stand-alone phones or be part of an IP PBX family. They offer the full range of phone features, such as call forwarding and conference calling, and also provide integration with applications such as Outlook for automatic phone dialing.

The first VoIP softphone was VocalTec's Internet Phone, which was introduced in 1995 (see Internet Phone). See VoIP, IP phone, IP PBX and IP telephony. See also software defined radio.