Alex Rodriguez becomes the fifth-youngest big leaguer to hit his 200th career home run, at 25 years and 289 days. Mel Ott accomplished the feat in 1934 at the youngest age (25 years, 144 days).

On May 13, 2001 — Alex Rodriguez becomes the fifth-youngest big leaguer to hit his 200th career home run, at 25 years and 289 days. Mel Ott accomplished the feat in 1934 at the youngest age (25 years, 144 days).

Source:
Baseball Reference May 13