High Efficiency Video Coding (HEVC), also known as H.265 and MPEG-H Part 2, is a proprietary video compression standard designed as part of the MPEG-H project as a successor to the widely used Advanced Video Coding (AVC, H.264, or MPEG-4 Part 10). In comparison to AVC, HEVC offers from 25% to 50% better data compression at the same level of video quality, or substantially improved video quality at the same bit rate. It supports resolutions up to 8192×4320, including 8K UHD, and unlike the primarily eight-bit AVC, HEVC's higher-fidelity Main 10 profile has been incorporated into nearly all supporting hardware.

While AVC uses the integer discrete cosine transform (DCT) with 4×4 and 8×8 block sizes, HEVC uses both integer DCT and discrete sine transform (DST) with varied block sizes between 4×4 and 32×32. The High Efficiency Image Format (HEIF) is based on HEVC.

In most ways, HEVC is an extension of the concepts in H.264/MPEG-4 AVC. Both work by comparing different parts of a frame of video to find areas that are redundant, both within a single frame and between consecutive frames. These redundant areas are then replaced with a short description instead of the original pixels. The primary changes for HEVC include the expansion of the pattern comparison and difference-coding areas from 16×16 pixel to sizes up to 64×64, improved variable-block-size segmentation, improved "intra" prediction within the same picture, improved motion vector prediction and motion region merging, improved motion compensation filtering, and an additional filtering step called sample-adaptive offset filtering. Effective use of these improvements requires much more signal processing capability for compressing the video but has less impact on the amount of computation needed for decompression.

HEVC was standardized by the Joint Collaborative Team on Video Coding (JCT-VC), a collaboration between the ISO/IEC MPEG and ITU-T Study Group 16 VCEG. The ISO/IEC group refers to it as MPEG-H Part 2 and the ITU-T as H.265. The first version of the HEVC standard was ratified in January 2013 and published in June 2013. The second version, with multiview extensions (MV-HEVC), range extensions (RExt), and scalability extensions (SHVC), was completed and approved in 2014 and published in early 2015. Extensions for 3D video (3D-HEVC) were completed in early 2015, and extensions for screen content coding (SCC) were completed in early 2016 and published in early 2017, covering video containing rendered graphics, text, or animation as well as (or instead of) camera-captured video scenes. In October 2017, the standard was recognized by a Primetime Emmy Engineering Award as having had a material effect on the technology of television.

HEVC contains technologies covered by patents owned by the organizations that participated in the JCT-VC. Implementing a device or software application that uses HEVC may require a license from HEVC patent holders. The ISO/IEC and ITU require companies that belong to their organizations to offer their patents on reasonable and non-discriminatory licensing (RAND) terms. Patent licenses can be obtained directly from each patent holder, or through patent licensing bodies, such as MPEG LA, Access Advance, and Velos Media.

The combined licensing fees currently offered by all of the patent licensing bodies are higher than for AVC. The licensing fees are one of the main reasons HEVC adoption has been low on the web and is why some of the largest tech companies (Amazon, AMD, Apple, ARM, Cisco, Google, Intel, Microsoft, Mozilla, Netflix, Nvidia, and more) have joined the Alliance for Open Media, which finalized royalty-free alternative video coding format AV1 on March 28, 2018.

The HEVC format was jointly developed by more than a dozen organisations across the world. The majority of active patent contributions towards the development of the HEVC format came from five organizations: Samsung Electronics (4,249 patents), General Electric (1,127 patents), M&K Holdings (907 patents), NTT (878 patents), and JVC Kenwood (628 patents). Other patent holders include Fujitsu, Apple, Canon, Columbia University, KAIST, Kwangwoon University, MIT, Sungkyunkwan University, Funai, Hikvision, KBS, KT and NEC.

In 2004, the ITU-T Video Coding Experts Group (VCEG) began a major study of technology advances that could enable the creation of a new video compression standard (or substantial compression-oriented enhancements of the H.264/MPEG-4 AVC standard). In October 2004, various techniques for potential enhancement of the H.264/MPEG-4 AVC standard were surveyed. In January 2005, at the next meeting of VCEG, VCEG began designating certain topics as "Key Technical Areas" (KTA) for further investigation. A software codebase called the KTA codebase was established for evaluating such proposals. The KTA software was based on the Joint Model (JM) reference software that was developed by the MPEG & VCEG Joint Video Team for H.264/MPEG-4 AVC. Additional proposed technologies were integrated into the KTA software and tested in experiment evaluations over the next four years.