In the United States, can the executor of a will be the sole beneficiary?
No state prohibits the executor of a will from being the sole beneficiary. There are generally rules in the various states that the executor must be over 18 and not judged incompetent; there may be rules against felons or non-residents being executors. A person could be excluded as executor in some states (e.g. Texas) if there is a conflict of interest, but being sole beneficiary is not a conflict of interest.