Gary J. Sullivan is an American electrical engineer who led the development of the H.264/AVC video coding standard and created the DirectX Video Acceleration (DXVA) API/DDI video decoding feature of the Microsoft Windows operating system platform. He was the chairman of the Joint Video Team (JVT) standardization committee that developed the H.264/AVC standard, and he edited large portions of it. He has also led and contributed to a number of other video and image related standardization projects such as extensions of ITU-T H.263 video coding and the standardization of JPEG XR image coding.

Dr. Sullivan is the rapporteur/chairman of the ITU-T Video Coding Experts Group (VCEG), a co-chairman of the video part of the ISO/IEC Moving Picture Experts Group (MPEG), and a co-chairman of the Joint Video Team (JVT), which is a joint project between the VCEG and MPEG organizations. He has led ITU-T VCEG (ITU-T Q.6/SG16) since 1996 and is also the ITU-T video liaison representative to MPEG and JPEG. In MPEG (ISO/IEC JTC1/SC29/WG11), in addition to his current service as a co-chair of its video work, he also served as the chairman of MPEG video from March 2001 to May 2002. In the Joint Video Team he was the chairman for the development of the next generation H.264/AVC video coding standard and its fidelity-range extensions (FRExt), and was a co-chairman for the development of the Scalable Video Coding (SVC) extensions. He is currently a co-chair of the Joint Collaborative Team on Video Coding which is developing the High Efficiency Video Coding standard.