right holder; rightful claimant; beneficiary
Legal and formal term for a person or entity that holds a right, such as a copyright holder, patent holder, or beneficiary of a claim.
著作権の権利者は、その作品の使用を許可できる。
The copyright holder can authorize the use of the work.
特許の権利者として、彼はライセンス料を受け取る。
As the patent right holder, he receives licensing fees.
権利者 is the general legal term for anyone holding a right, whereas 有権者 in this sense is specifically tied to the right to vote.
co-creditor; joint obligee
Compound of 権利 (けんり, 'right') + 者 (しゃ, 'person'). The word follows the standard pattern of adding 者 to a noun to indicate the person associated with that noun.