Luna Lovegood is a witch in Ginny's year who is considered a bit weird by her classmates. She comes by this reputation honestly: Luna simply isn't like the other kids at all. She dresses unusually, she proclaims her strange beliefs openly, and in some ways she seems to be completely out of touch with what's going on around her. She has a somewhat bizarre sense of appropriate social behavior. For example, for a Quidditch match where the students wave banners and wear rosettes in team colors, Luna sports a hat with a life-sized lion's head on it which roars very realistically (OP19). While commentating a match she ignored such mundane things as the score and speculated on possible ailments afflicting the players (HBP19).

Luna takes after her father in having a very open mind and consequently a number of unusual beliefs. Luna also has some unusual habits: putting her wand behind her ear for safekeeping, wearing odd items as jewelry such as a necklace of butterbeer corks and radishes for earrings. As it turns out, the "radishes" are Dirigible Plums, which the Lovegoods cultivate and believe to "enhance the ability to accept the extraordinary" (DH20).

Luna is often the butt of jokes. Her peculiar habits and odd beliefs make her the target of teasing and ridicule. She is called Loony Lovegood behind her back. Others steal her possessions all through the year and she is forced to put up notices on the last day of term, asking for her things back. Through it all, Luna is surprisingly patient and accepting. She doesn't fight back or even seem to notice, although she is certainly aware of much of the teasing. She knows that her nickname is Loony, for example, but mentions it to Harry in a very matter-of-fact way (OP38).

Harry met Luna for the first time aboard the Hogwarts Express on September 1, 1995. He, Ginny, and Neville shared a compartment with her on the train (OP10). She was reading a copy of The Quibbler magazine upside down. She informed the others that her father is the editor of The Quibbler, a magazine which most in the Wizarding World consider a joke. She laughed a little too loud; she stared at the other kids, and generally made an odd traveling companion. Harry privately thought, when Cho Chang happened by their compartment to say hello, that he would much rather have been sitting with "cooler" kids than Luna and Neville.

Luna can see Thestrals (OP10), having witnessed her mother's death when she was nine (OP38). Harry was unsure about her, especially when it turned out that she was the only one that he knew who could see the Thestrals. She told him that he was as sane as she was, which wasn't all that comforting to hear. Over the course of the year, Luna proved to be a faithful friend to Harry and his friends. She supported the Gryffindor team against every other house except Ravenclaw. She took a stand in favor of believing Harry in front of a group of other fourth and fifth year students. She joined Dumbledore's Army and worked hard. That training paid off in the Battle of the Department of Mysteries, during which she fought bravely against the Death Eaters in June 1996 -- the only non-Gryffindor member to do so (OP35).

Luna Lovegood, Perhaps Luna's greatest moment, however, came at the very end of the 1995-1996 school year. Harry was suffering terribly from the loss of his godfather and he spent a frantic few hours trying to find some way to contact Sirius. He tried methods similar to séances and contacted ghosts to try to talk to the dead but found comfort in none of these things. When Luna encountered Harry, she spoke of the comfort which she has in knowing that she will see her dead mother again, which brought true comfort to Harry (OP38). Just like being able to see Thestrals, Luna and Harry both heard whispers from behind the veil in the Department of Mysteries (OP35).

Luna seems to be more serene and composed than most of her peers. She often stares off into the distance and seems detached from what is going on around her. Her deeply-held beliefs, although not understood or accepted by those around her, do give her a certain dignity. By the end of the 1995-1996 school year, she was much more accepted as a friend and comrade by Harry, Ron, and Hermione.

Luna lives with her father Xenophilius Lovegood, in a house shaped like a "rook" or round castle, near Ottery St. Catchpole. The interior is decorated eccentrically as one would expect from Luna, with bright paintings on everything. On her bedroom ceiling she painted pictures of Harry, Ron, Hermione, Ginny, and Neville's faces and entwined them with a golden chain of the repeated word "friends". This touched Harry deeply (DH20).

Her mother was a "quite extraordinary" witch who loved to experiment. When Luna was nine years old, one of her mother's spells went rather horribly wrong and she was killed. Luna still misses her terribly sometimes, but she finds comfort knowing that she'll see her again one day in the afterlife (OP38). Luna resembles her mother (DH20).

Luna came into her own during her sixth year at Hogwarts. With Harry, Ron, and Hermione gone from school, she joined Ginny and Neville to revive Dumbledore's Army and resist the Death Eaters' influence at Hogwarts. She was kidnapped on the Hogwarts Express on her way home for the Christmas holidays (DH25) because of what Mr. Lovegood had been writing in The Quibbler, and imprisoned in the cellar at the Malfoy Mansion along with Ollivander. She was helpful in their efforts to escape the Malfoy Mansion, and then fought bravely, again, at the Battle of Hogwarts (DH31).

After leaving Hogwarts, Luna went on to become a very famous wizarding naturalist, studying new species of creatures and marrying a fellow naturalist, named Rolf, a grandson of the great Newt Scamander, and had twin boys named Lorcan and Lysander (BLC, YL).

It was Luna who suggested the lost diadem of Ravenclaw might be the remaining Horcrux (DH29). She was fond of reciting the phrase that is inscribed on the diadem: “Wit without measure is man’s greatest treasure.” Perhaps in Luna’s case, the phrase would be better quoted as “Wit and faith and love are man’s greatest treasure. (OP10)” Luna possesses all of these without measure and has proven to be a treasure indeed.

Credit to HP-Lexicon