Skype (pron-en?ska?p) is a software application (application software) that allows users to make voice calls over the Internet (voice over Internet Protocol). Calls to other users within the Skype service are free, while calls to both traditional landline telephones (landlines) and mobile phones can be made for a fee using a debit-based user account system. Skype has also become popular for its additional features which include instant messaging, file transfer, and video conferencing.

Skype was developed by Estonian developers Ahti Heinla, Priit Kasesalu and Jaan Tallinn, who had also originally developed the peer-to-peer file sharing software Kazaa.

Skype Limited, the company that operates Skype, was founded in 2003 by Niklas Zennstr�m and Janus Friis with headquarters in Luxembourg.

eBay acquired Skype Limited in September 2005 and in April 2009 announced plans to spin it off in a 2010 IPO.