The legal status of cryptoassets as property has been widely accepted, but it remains unclear who owns a cryptoasset. This article explores the determination of the owner of a cryptoasset. It argues that under the doctrine of deemed ownership, a person in possession of a thing is deemed or presumed to be its owner unless there is evidence to the contrary. The cryptographic control of cryptoassets is equivalent or analogous to the physical possession of tangible things. Thus, a private key holder who has cryptographic control of a cryptoasset is presumed to be the owner of the cryptoasset. A person without cryptographic control can prove ownership of the cryptoasset in the hands of a different person if they can follow or trace the cryptoasset into the hands of the controller and they are entitled to claim ownership over the followed or traced cryptoasset.