He is the champion of this year's tennis tournament.
優勝者にはトロフィーが贈られた。
A trophy was awarded to the winner.
優勝者 specifically means the overall champion of a tournament, whereas 勝者 can refer to the winner of any single match or confrontation.
メダリスト covers anyone who wins a medal (gold, silver, or bronze), while 優勝者 refers specifically to the first-place winner or champion.
優勝者 specifically means the champion of a tournament or competition, a narrower sense than the general 'winner' meaning of ビクター.
優勝者 is the neutral, everyday word for the winner of a tournament, while 覇者 carries a grander, more dramatic tone of supremacy.
Compound of 優勝 (championship, victory) and 者 (person). The exact historical derivation is straightforward; the word follows a common pattern for forming agent nouns.