One who pronounces a valedictory address; especially, in American colleges, the student who pronounces the valedictory of the graduating class at the annual commencement, usually the student who ranks first in scholarship
Properly: The individual in a graduating class who delivers the farewell or valedictory address, usually the person who graduates with the highest grades
A valedictorian is the student who has the highest marks in their class when they graduate from high school, college, or university, and who gives a speech at their graduation ceremony. the student who has received the best marks all the way through school, and usually makes a speech at the graduation ceremony