noun
opposing role; partner
Refers to a person who plays a complementary or opposing role in a performance, story, or pairing. Often used in theater, film, and dance contexts for a co-star or counterpart.
彼女はその舞台で主役の相手役を演じた。
She played the lead's partner in that stage production.
映画の相手役に誰を選ぶかが重要だ。
Choosing who will play the co-starring role in the movie is important.
共演者 is a more general term for a co-performer, while 相手役 specifically implies a paired or complementary role, often with a dramatic relationship.
Compound of 相手 (partner, opponent) and 役 (role).