Viber is an instant messaging and Voice over IP (VoIP) app for smartphones developed by Viber Media. In addition to instant messaging, users can exchange images, video and audio media messages. The client software is available for Mac OS, Android, BlackBerry OS, iOS, Series 40, Symbian, Bada, Windows Phone, and Microsoft Windows. A Linux version is available for Ubuntu 64-bit. Viber works on both 3G/4G and Wi-Fi networks. It first requires installation on a phone in order to work on a desktop operating system environment. Viber has over 100 million monthly active users from its 280 million global registered users.

Viber was founded by four Israeli partners: Talmon Marco, Igor Megzinik, Sani Maroli and Ofer Smocha, with Talmon Marco as its CEO. Viber was initially launched for iPhone on December 2, 2010, in direct competition with Skype. A pre-release version for Android appeared in May 2011 but was restricted to 50,000 users; an unrestricted version was released on July 19, 2012. Viber for BlackBerry and Windows Phone devices was launched on May 8, 2012. On reaching 90 million users on July 24, 2012, group messaging service and HD Voice engine were added to both Android and iPhone applications. Applications for Nokia`s Series 40, Symbian and Samsung`s Bada platform were also announced on the same day.

Initially, the voice calling feature was only available for iPhone and Android applications, with a promise that voice would be added in upcoming versions for Bada, Symbian and Windows Phone applications, with no mention of either Series 40 or Blackberry OS. The limitation seems to lie in the core of Blackberry OS and Series 40 which does not have easy support for VoIP apps.

On September 22, 2012, HD quality phone calls and hold group-messaging sessions were made available for Windows Phone but only for Nokia users, as part of exclusive partnership with Nokia. Viber with voice was officially released for all Windows Phone 8 devices on April 2, 2013.

In August 2013, Viber for Linux was released as a public beta and in August 2014 a final version. Initially, only 64-bit binaries were made available for download.

On February 13, 2014, Rakuten announced they had acquired Viber for $900 million.

Viber Media is a Las Vegas and Cyprus-registered company with its development centers in Belarus and Israel. The company was founded by Talmon Marco and Igor Megzinik, who are friends from the Israel Defense Forces. The company is run from Israel, with much of its development outsourced to Belarus in order to lower labor-costs.

Founded in 2010, the company is co-owned by its four Israeli founders: Talman Marco, Igor Megzinik, Sani Maroli and Ofer Smocha, who have each increased their investment by over 30 times on the startup's $900 million sale to Rakuten.

Marco and Megzinik are also co-founders of the P2P media and file-sharing client iMesh.

The company originally didn't generate revenues, but announced it would start generating revenues in 2013 via a "sticker store". The company is funded by individual investors, who Marco has described as "friends and family". As of May 2013, $20M had been invested in the company.