Felix Felicis<ref>Pronounciation: feːliks feːlikis; both words are derived from classical Latin and both mean lucky, hence the reason why this potion is often referred to as "the luck potion."</ref> is a potion introduced to Harry Potter's sixth year Potions class by Horace Slughorn. The potion brings extraordinary luck to anyone who drinks it. Its use is, therefore, banned from all kinds of betting and gaming (HBP9). If taken in excess, it causes "giddiness, recklessness, and dangerous overconfidence," and therefore must be taken sparingly.
Felix Felicis is a complicated potion. It takes six months to be prepared; "you've got to let it stew" (HBP24). It is the color of molten gold, and when it sits, large drops leap from the surface like goldfish (HBP9).
Harry wins a small bottle of this potion as a prize in a potion-brewing contest that Professor Slughorn holds. He wins this competition with small hints given in the mysterious Half-Blood Prince's textbook.
Harry pretends to give Ron Felix Felicis before a Quidditch match. Ron performs admirably, believing that he has taken the potion. After the match, Hermione berates Harry for using an illegal potion, and Harry reveals that he did not actually add the potion to Ron's drink (HBP14).
Harry takes Felix Felicis in order to obtain the Horcruxes memory from Slughorn; under its influence, he takes Slughorn to Aragog's burial and gets him drunk. By the end of the night, Slughorn has given him the memory (HBP22).