Ellaria Sand is a fictional character in the A Song of Ice and Fire series of high fantasy novels by American author George R. R. Martin and its television adaptation Game of Thrones, where she is portrayed by Indira Varma.

Ellaria first appears in the third novel A Storm of Swords (2000). She is only mentioned in A Feast for Crows (2005), but returns in A Dance with Dragons (2011). She is the paramour to Oberyn Martell and mother to several of his bastard daughters, the Sand Snakes. After the death of her lover in a duel at the hands of Ser Gregor Clegane, she is sent into deep mourning, though she pushes for Oberyn's brother Doran Martell to sue for peace, seeking an end to the cycle of revenge.

In the television adaptation, Ellaria becomes a composite character of her book counterpart and Oberyn's niece, Arianne Martell as she is seeking for Dorne to go to war against the Lannisters for their crimes against House Martell. However, in stark contrast to Arianne, Ellaria is portrayed as a ruthless and vengeful killer who seeks to murder the innocent Myrcella Baratheon, instead of crowning her to oppose Cersei and Tommen, and then slays Oberyn's remaining family so that she can seize power in Dorne. Though Varma's performance was praised, Ellaria's story arc in the series was met with an overwhelmingly negative critical reception.

Ellaria Sand is a bastard of Harmen Uller, head of House Uller and Lord of Hellholt in Dorne. Dorne's views and customs towards children born out of wedlock differ from those of the rest of Westeros, where bastards are often discriminated against. She is the paramour of Oberyn Martell, as even in Dorne a Prince cannot marry a bastard. She is the mother of the youngest four Sand Snakes (Oberyn's bastard daughters). Like Oberyn, she is bisexual.

In the novels, Ellaria Sand is mostly a background character. She is not a point-of-view character; rather, her actions are witnessed and interpreted through the eyes of other people, such as Tyrion Lannister, Arianne Martell, and Areo Hotah.

Ellaria comes with Oberyn to King's Landing, as part of Tyrion Lannister's efforts to win them to the Iron Throne. Oberyn, however, clearly wants revenge for his sister's death, apparently committed on the orders of Tywin Lannister, during King Robert's rebellion. Oberyn wants Ellaria to sit with him at Joffrey Baratheon's wedding, causing trouble when Olenna Tyrell calls her "the serpent's whore". Later, when Tyrion is condemned for poisoning Joffrey Baratheon, Oberyn acts as his champion in a trial by combat against Ser Gregor Clegane, who had raped and murdered Oberyn's sister, Elia Martell, during the Sack of King's Landing. Oberyn wounds Gregor with a poisoned spear but is killed by Gregor. Afterwards, Ellaria returns to Dorne.

Gregor Clegane apparently dies of the poison after spending days in agony (Oberyn having treated the poison to work slowly). His skull is sent to Dorne, where Oberyn's brother, Doran Martell, the ruling Prince of Dorne, sees it. Despite Gregor and Tywin's deaths, Oberyn's bastard daughters want revenge. Ellaria argues against revenge, saying all those they want revenge against are dead and the Lannisters they are now targeting took no part in their kin's deaths. She reminds them Oberyn died trying to avenge his sister's death and worries they too will die, if they seek vengeance. Doran sends her back to her father, Lord Harmen Uller of Hellholt with her youngest daughter Loreza Sand.

Ellaria Sand is played by the British actress Indira Varma in the television adaption of the series of books. She won the Empire Hero Award along with the rest of the cast in 2015. She was also nominated, along with the rest of the cast for Screen Actors Guild Award for Outstanding Performance by an Ensemble in a Drama Series in 2016.