Kagamine Rin & Len (鏡音リン・レン Kagamine Rin & Len), are humanoid personas voiced by a singing synthesizer application developed by Crypton Future Media, headquartered in Sapporo, Japan. They use Yamaha Corporation's Vocaloid 2 and Vocaloid 4singing synthesizing technology. Their voices are sampled by Asami Shimoda. They have performed at live concerts onstage as animated projections.

Their names are derived from the concept of 'left' and 'right', like on earphones. Their surnames came from the Japanese words for "mirror" (鏡 kagami) and "sound" (音 ne).