.3g2 is a file extension for a video in 3GP format. This is a multimedia container format used be mobile phones. 3GP is a simplified version of the MP4 format and was designed to make file size smaller so mobile phones could support video.

There are two standards for this format: 3GPP, with the extension .3gp, and 3GPP2, with the file extension .3g2. 3GPP and 3GPP2 stand for 3rd Generation Partnership Program and 3rd Generation Partnership Program 2 respectively. 3GPP files are for GSM based phones, and 3GPP2 files are for CDMA based devices.

The .3g2 files can store the same video and most of the audio streams used in .3gp file format. In addition .3g2 stores audio streams as EVRC, EVRC-B, EVRC-WB, 13K - (QCELP), SMV, VMR-WB, which was specified for use in ISO base media file format.

The .3g2 specification also defined some enhancements to 3GPP Timed Text.