The Sinsk Formation is a geologic formation in Central Siberia, Russia, exposed along the Lena River. It preserves fossils dating back to the Botomian stage of the Cambrian. It notably contained the Sinsk Algal Lens, a Lagerstätte which preserved some soft-bodied animals that would not typically be preserved as fossils. However, the Sinsk Algal Lens has largely been destroyed by commercial fossil collectors.