Skype's VoIP phone service is set to be available on the Apple iPhone and iPod, along with several BlackBerrys.
The iPhone and Touch support will begin immediately, and BlackBerry support should be available in the coming months.
Skype now has more than 400 million global users, and the number continues to rise as they expand further onto mobile phones.
The company previously announced its software will be available for Nokia and Microsoft Windows Mobile phones, and Google Android operating system support.
Skype looks to better compete with Verizon Wireless and AT&T, and offering free software for the iPhone will give it an important boost for future user battles.
Similar to other apps offered through the App Store, Skype will be limited to Wi-Fi support only, which means phone owners can't use the AT&T data network when using the program.
Users will be able to call other mobile Skype users -- or computer users -- for free, while calls to landlines will be available for a fee.
Skype video is popular among PC Skye users, but it remains unknown if the company will offer the feature through the iPhone app.
