In criminal and property law, theft by finding occurs when someone chances upon an object which seems abandoned and takes possession of the object, but fails to take steps to establish whether the object is genuinely abandoned and not merely lost or unattended before taking it for themselves. In some jurisdictions, the crime is called "larceny by finding" or "stealing by finding".
In property law, lost, mislaid, and abandoned property are categories of the common law of property which deals with personal property or chattel which has left the possession of its rightful owner without having directly entered the possession of another person. Property can be considered lost, mislaid, or abandoned depending on the circumstances under which it is found by the next party who obtains its possession.
An old saying is that "possession is nine-tenths of the law", dating back centuries. This means that in most cases, the possessor of a piece of property is its rightful owner without evidence to the contrary. More colloquially, these may be called finders, keepers. The contradiction to this principle is theft by finding, which may occur if conversion occurs after finding someone else's property.