a former incumbent; the person who previously held a position (i.e., one's predecessor).
彼は前任の部長から業務を引き継いだ。
He took over the duties from the previous department manager.
前任者が残した資料はとても役に立った。
The materials left by the predecessor were very helpful.
前任と比べて、今の体制は効率的だ。
Compared with his predecessor, the current system is more efficient.