Multimedia is increasingly becoming the "biggest big data" as the most important and valuable source for insights and information. It covers from everyone’s experiences to everything happening in the world. As such, multimedia big data is spurring on tremendous amounts of research and development of related technologies and applications. The IEEE International Conference on Multimedia Big Data (BigMM), jointly sponsored by IEEE-TCMC (Technical Committee on Multimedia Computing) and IEEE-TCSEM (Technical Committee on Semantic Computing), is the world's premier forum of leading scholars in the highly active multimedia big data research, development and applications. The first BigMM conference, with the theme "Multimedia: The Biggest Big Data", will be held in Beijing, China, from April 20 to 22, 2015, hosted by Peking University.