Monarch butterfly
No single individual makes the whole round trip. The monarch is famous for its southward migration and northward return in summer. The migration north spans the life of three to four generations of the butterfly. A longer-lived "super generation" flies from the northern-most parts of the butterfly's range in Canada all the way to Mexico. It overwinters in the south, and breeds in the spring to start the next generation flying north. The following reference gives a map of the migration routes.