How long is the worlds longest rainbow loom single chain?

753.39 meters. It was made by 7 year old Ben Mooney. It took him approximately one month to make it. I hope this info was useful! :-)

A reliable answer is not possible. At any given time, someone, somewhere in the world, is looming a single chain that could be longer than any made previously. Also, most of the Rainbow Loom projects being made are not reported or recorded by any official agency, so there is no way to know how long the longest single chain might be, or when or where it might be made.