What is the name of the potion that grants the drinker perfect luck for a period?

The potion that grants the drinker exceptionally good luck for a period is Felix Felicis. Also called Liquid Luck, it makes the drinker unusually fortunate while its effects last.

Felix Felicis appears most prominently in Harry Potter and the Half-Blood Prince. Professor Slughorn gives Harry a small bottle as a prize for brewing the best Draught of Living Death, though Harry later uses it to encourage Professor Slughorn to reveal an important memory about Tom Riddle. Harry also gives some to Ron before a Quidditch match, although Ron only believes he has taken it.

The potion is powerful but not a universal solution. Overuse can cause dizziness, recklessness, and dangerous overconfidence, and it is banned from use in official examinations and sporting events. It also cannot simply create knowledge or skill; it improves circumstances and nudges the drinker toward fortunate choices.

Felix Felicis is commonly confused with Amortentia, which creates powerful infatuation, or Polyjuice Potion, which changes appearance. Its name combines Latin words associated with happiness and good fortune.