When it comes to describing a "beautiful youth," there are numerous synonyms to choose from. One of the most common synonyms is "handsome," which is often used to describe men with attractive physical features. "Radiant" is a word that can be used to describe the glowing energy and aura of someone, while "captivating" emphasizes a person's ability to draw in and hold the attention of others. Additionally, the words "dazzling" and "sparkling" can convey a sense of enchantment and glamour surrounding a young person. Other synonyms might include "stunning," "charismatic," "beaming," or "charming," depending on the context and specific attributes being emphasized.