The proper name is the
Many Worlds interpretation.
If you click on the link, you'll see that "Many worlds"-like interpretations are now considered fairly mainstream within the quantum physics community. For example, a poll of 72 leading physicists conducted by the American researcher David Raub in 1995 and published in the French periodical Sciences et Avenir in January 1998 recorded that nearly 60% thought many worlds interpretation was "true".