Lyra Belacqua (/ˈlaɪrə bəˈlɑːkwə/ LY-rə bə-LAH-kwə), later known as Lyra Silvertongue, is the heroine of Philip Pullman's trilogy His Dark Materials. In His Dark Materials Lyra is a young girl who inhabits a universe parallel to our own. Brought up in the cloistered world of Jordan College, Oxford, she finds herself embroiled in a cosmic war between Lord Asriel on one side, and a deity figure known as The Authority and his Regent, Metatron, on the other. Lyra also features prominently in the subsequent trilogy The Book of Dust.

Lyra Belacqua, aged around eleven at the beginning of the trilogy, is the daughter of Lord Asriel and Marisa Coulter in a fictional Oxford, similar to our own. She is being brought up at Jordan College, where the scholars, professors and servants treat her as an adopted daughter. She has been raised believing that her parents died in an airship crash, and that Lord Asriel is her uncle; she later learns the truth from John Faa, leader of the Gyptians. Lyra spends much of her time socialising with other children of the city, sometimes harmoniously, frequently mock-violently, and often in order to avoid schoolwork. Her closest friend among the other children is a Jordan kitchen boy named Roger Parslow, who disappears early in Northern Lights. The search to find Roger, and other children, is Lyra's motivation throughout much of Northern Lights.

Lyra is described as having wavy dirty-blonde hair and pale-blue eyes, and is thin and short for her age. Lyra is unruly and tomboyish and her complete disregard for her appearance and personal hygiene exasperates her adult carers. She receives a scant and haphazard education at the hands of Jordan scholars, being neither interested in study nor officially a student of the college. However, she is highly intelligent, and is particularly talented at deceiving others; she is capable of making up complex yet plausible lies on the spur of the moment. Initially she uses this talent to avoid punishment by her guardians, and to entertain and deceive other children, but later in the series employs it to save her own life and the lives of others. She deceives Iofur Raknison, king of the panserbjørne ("armoured bears" in Danish) of Svalbard, by suggesting that she can become his dæmon if Iofur defeats Iorek in combat. Tricking a panserbjørn was a feat that her friend Iorek Byrnison had believed to be impossible for a human, and her success prompts Iorek to informally christen her "Silvertongue", which is the surname by which she is known in The Secret Commonwealth.

The character's first name comes from Lyra Davidica, which means "harp of David." Lyra Davidica is the title of a hymnal collection, but Pullman mistook it for the author's name of an Easter hymn he liked, as it was printed under the number of the hymn. He later realized it wasn't actually a person’s name, though due to the popularity of the character, it has now become one. The name is also a pun on the word "liar", and the connection between these two words is emphasized by the text.

Lyra's surname, Belacqua, is the name of a character in Dante's Divine Comedy, a soul in the ante-purgatory, representing those who wait until the last opportunity before turning to God. The mood in the ante-purgatory is said to be one of helplessness, nostalgia, and yearning – Belacqua and the other souls in ante-purgatory are caught between two worlds and lack clear understanding of themselves. Whether this has any connection to Lyra is not known.

Lyra's dæmon, Pantalaimon /ˌpæntəˈlaɪmən/, is her dearest companion, whom she calls "Pan". In common with dæmons of all children, he can take any animal form he pleases; he first appears in the story as a dark brown moth. His name is a given male name in the Eastern Orthodox world (Παντελεήμων Panteleēmon), which in Greek means "all-compassionate". He changes into many forms throughout the series, ranging from a dragon to an eagle, but his favourite forms are a snow-white ermine, a moth, a wildcat, and a mouse. At the end of the trilogy, as Lyra is entering adulthood, Pantalaimon finds his final form when Will Parry touches him, and is later described as a beautiful pine marten, red-gold in colour with a "patch of cream-white fur" on his throat.

Pantalaimon is portrayed as a cautious and level-headed counterpoint to Lyra's impulsive, inquisitive, and sometimes reckless character.

Lyra must separate from Pantalaimon when she enters the Land of the Dead in The Amber Spyglass, causing extreme pain to both of them; Pantalaimon avoids Lyra for a while afterwards. However, surviving this separation allows the two to move great distances from one another, an ability only witches and shamans generally possess in her world.