Multimedia experiences allow us to access other worlds, to live other people's stories, to communicate with or experience alternate realities. Different spaces, times or situations can be entered thanks to multimedia contents and systems, which coexist with our current reality, and are sometimes so vivid and engaging that we feel we are living in them. Advances in multimedia are making it possible to create immersive experiences that may involve the user in a different or augmented world, as an alternate reality. AltMM 2016, the 1st International Workshop on Multimedia Alternate Realities at ACM Multimedia, aims at exploring how the synergy between multimedia technologies and effects can foster the creation of alternate realities and make their access an enriching, valuable and real experience. The workshop program will contain a combination of oral and invited keynote presentations, and poster, demo and discussion sessions, altogether enabling interactive scientific sharing and discussion between practitioners and researchers.@en