Fire and Sword (German: Feuer und Schwert: Die Legende von Tristan und Isolde) is a 1981 romantic drama film directed by Veith von Fürstenberg [de]. It is based on the legend of Tristan and Isolde, played by Christoph Waltz (in his first leading credited film role) and Antonia Preser. Leigh Lawson and Peter Firth also star. Set during a raging war between Cornwall and Ireland, the film explores themes on conflict between magic and religion, violence, and destruction.

Principal photography took place from July to November 1980. It was filmed in Ireland at the same location as Excalibur (1981), another Arthurian film, and reused the stuntmen and horses from that production. Critics praised its cinematography, for which it won an award at the 1983 Sitges Film Festival, but criticised the script, Waltz's and Preser's performances, and its interpretation of the source material.

As war rages between Cornwall and Ireland, the Cornish knight Tristan defeats Morholt, a formidable Irish warrior, in combat. Tristan himself is gravely injured and drifts out to sea, eventually landing on the coast of Ireland. He pretends to be a minstrel named Tantris and is treated at a convent by the Irish princess Isolde, who is disguised as a maid. As Tristan recovers, they fall in love—even after Isolde examines his sword and deduces that he killed Morholt—and when he is called back to the Cornish court, he promises to return for her.

Tristan's uncle, King Marke of Cornwall, plans to establish peace through a political marriage to Isolde. Tristan volunteers to escort the princess to Cornwall. When he arrives in Ireland again, he and Isolde are each astounded to learn of the other's true identity. Tristan, who is fiercely loyal to the king, rejects Isolde's suggestion that they run away together. She prepares a potion that will cause its drinkers to fall senselessly in love forever and mixes it into both her and Tristan's wine. In Cornwall, Isolde weds Marke immediately but the potion exerts its influence on her and Tristan. They regularly meet in secret with the assistance of their servants, Brangäne and Gorvenal. Andret, a court advisor who seeks the throne, eventually exposes their tryst.

Confronted with the reality about his nephew and his wife, Marke orders their imprisonment and execution. Tristan escapes and Isolde is spared with the help of Tristan's friend Dinas. She is sentenced to live with a leper but is rescued by Tristan, and the lovers flee Cornwall. Three years later, Cornwall is under attack by the Irish, led by the traitorous Andret. Dinas finds Tristan and Isolde and urges them to return to the court and reconcile with Marke. Though Tristan is unwilling, Isolde agrees because she feels responsible for the resumption of the war. She returns to Cornwall and undergoes trial by ordeal, holding a red-hot iron to establish her innocence and restore peace.

Tristan travels to Brittany alone. He rescues a peasant woman from robbers and cynically names her "Isolde". Some time later, he is mortally wounded and sends Gorvenal to ask Isolde of Ireland to visit him on his deathbed. Gorvenal returns to Cornwall, where Andret has taken the throne. Marke learns of Gorvenal's plan and agrees to mobilise his knights to safely escort Isolde out of Cornwall. Andret is killed in the ensuing commotion. As Isolde sails to Brittany, the jealous Breton maid lies to Tristan about the color of the sails on the returning boat, implying that Gorvenal's mission was unsuccessful. He dies, and when Isolde arrives to see him, she collapses in grief and joins him in death.

In his analysis of the film, the literary scholar Stefan Keppler-Tasaki commented that it is "clearly critical of religion". The Irish nuns initially consider leaving Tristan to die of his injuries, citing a lack of room at their convent. The film then juxtaposes religion and sorcery, emphasising Isolde's powers as an sorceress as she heals Tristan with the use of magical herbs. Other elements of the film also symbolise the subversion of religion. During his escape, Tristan crashes through and destroys a stained glass icon of Saint George, patron of England, and Marke noticeably sets aside his personal wooden cross when he is rejected by Isolde. There is no mention of the Christian God; rather, Isolde describes an omnipotent goddess of love in reference to her and Tristan's magic-induced love.

Isolde's skills in magic are a recurring element, notably as she brews the love potion that she and Tristan later drink. Her preparation of the potion is a distinctive plot element among film depictions of Tristan and Isolde (in the 1981 film Lovespell, she similarly adds the potion with knowledge of its effects, but it was given to her by her guardian). She is characterised as "the magical catalyst of the story" and her magic elevates the importance of her role above Tristan's. The literary scholar Alain Kerdelhue suggested that the film could have alternatively been titled Isolde la Sorcière (French for Isolde the Sorceress) for its emphasis on Isolde as a magical figure.