Who is the youngest golfer to win one of the men's major championships (British Open, U.S. Open, PGA Championship, The Masters) of professional golf? All-time, the youngest major winner is 17-year-old Young Tom Morris. Since 1900, the youngest is 19-year-old John McDermott. And in the modern era — whether you define "modern" as "post-World War II" (since 1946) or "since 1970" — the youngest is 21-year-old Tiger Woods.