noun
finish line; goal line
The line marking the end of a race or competition.
彼は最初に決勝線を越えた。
He crossed the finish line first.
ゴール is a more general term for a goal or finish point, while 決勝線 specifically refers to the physical line in a race.
Compound of 決勝 (kesshō, 'decision of a contest') + 線 (sen, 'line').