3GP (3GPP file format) is a multimedia container format defined by the Third Generation Partnership Project (3GPP) for 3G UMTS (Universal Mobile Telecommunication System) multimedia services. It is used primarily on 3G mobile phones but can also be played on some 2G and 4G phones. 3GP is a required file format for video and associated speech/audio media types and timed text (including closed captioning) in ETSI 3GPP technical specifications for IP Multimedia Subsystem (IMS), Multimedia Messaging Service (MMS), Multimedia Broadcast/Multicast Service (MBMS) and Transparent end-to-end Packet-switched Streaming Service (PSS).

3G2 (3GPP2 file format) is a multimedia container format defined by the 3GGP2 for 3G CDMA2000 multimedia services. It is very similar to the 3GP file format, but has some extensions and limitations in comparison to 3GP.

The 3rd Generation Partnership Project (3GPP) is a collaboration between groups of telecommunications associations, known as the Organizational Partners. The purpose of 3GPP was to make a globally applicable third-generation (3G) mobile phone system specification within the scope of the International Mobile Telecommunications-2000 project of the International Telecommunication Union (ITU). 3GPP standardization encompasses Radio, Core Network and Service architecture. The project was established in December 1998.

The 3GP and 3G2 file formats are both structurally based on the ISO base media file format defined in ISO/IEC 14496-12 – MPEG-4 Part 12, but older versions of the 3GP file format did not use some of its features. 3GP and 3G2 are container formats similar to MPEG-4 Part 14 (MP4), which is also based on MPEG-4 Part 12. The 3GP and 3G2 file formats were designed to decrease storage and bandwidth requirements to accommodate mobile phones. 3GPP file format was designed for GSM-based phones and may have the filename extension .3gp. 3GPP2 file format was designed for CDMA-based phones and may have the filename extension .3g2. Some cell phones use the .mp4 extension for 3GP video.

Most 3G-capable mobile phones support the playback and recording of video in 3GP format (memory, maximum file size for playback and recording, and resolution limits exist and vary). Some newer/higher-end phones without 3G capabilities may also playback and record in this format. Audio imported from CD onto PlayStation 3 when it is set to encode to the MPEG-4 AAC codec copies onto USB devices in the 3GP format. The Nintendo DSi supports .3gp on an SD card.

When transferred to a computer, 3GP movies can be viewed on Linux, Mac and Windows platforms with MPlayer and VLC media player, making possible the transcription and archiving of filmed material. Programs such as Media Player Classic, K-Multimedia Player, Totem, Real Player, QuickTime and GOM Player can also be used. 3GP files can be encoded and decoded with open source software FFmpeg.