Refers to a person or entity that holds or occupies something, such as property, a position, or a right. Often used in legal or formal contexts.
Who is the possessor of this land?
Disposing of property whose occupant is unknown takes time.
居住者 specifically means a resident or inhabitant, whereas 占有者 can refer to any kind of occupant or possessor, not necessarily living there.
Compound of 占有 (せんゆう, 'possession, occupation') + 者 (しゃ, 'person'). The term is transparently derived from its components.