Merlin is a 1998 two-part television miniseries starring Sam Neill as Merlin, recounting the wizard's life in the mythic history of Britain. Loosely adapted from the legendary tales of Camelot, the plot adds the antagonistic Queen Mab and expands Merlin's backstory before the birth of King Arthur. The sequel Merlin's Apprentice followed in 2006.

Part 1

Merlin, an elderly man telling his life story, describes a Britain faced with invasions and tyrant kings increasingly cruel to the people. King Constant, the first Christian King of England, is executed by Vortigern, who immediately takes the crown and proclaims himself king. Fey goddess, Queen Mab, seeks to reclaim her power by drawing people back to worship The Old Ways. To do so, she creates a wizard named Merlin, whom she intends to champion her crusade. Merlin's mother dies giving birth to him, and he is raised by his aunt, Ambrosia, who left the Old Ways and has since converted to Christianity.

Now a teenager, Merlin recounts to Ambrosia how he rescued a nobleman's daughter, Nimue, from drowning by magically growing a branch. Ambrosia tells him of his past, and he is sent to Mab to begin training with Frik, Mab's gnome servant. Despite great aptitude, however, Merlin has little interest in helping Mab's crusade to restore the Old Ways, infuriating her. Merlin discovers from the Lady of the Lake, Mab's sister, that Mab let his birth mother die and that Ambrosia is terminally ill. Mab reaches Ambrosia's home before Merlin, but when Ambrosia refuses to convince Merlin to return to Mab, Mab lashes out, mortally injuring Ambrosia. Enraged, Merlin tries to attack Mab but can't defeat her. She coldly dismisses the deaths of his mother and Ambrosia as "casualties of war" and vows that Merlin will help her. Merlin makes a blood oath to use his powers only to defeat Mab.

Many years later, King Vortigern is unable to trust even his closest allies, including Nimue's father Lord Ardent. Paranoid that Ardent will defect to Uther Pendragon, King Constant's son and heir to the throne, Vortigern has Nimue imprisoned, threatening to have her executed if Ardent betrays him. Wanting to keep Nimue safe, Ardent begrudgingly agrees. Angered that his new castle keeps collapsing, Mab convinces Vortigern his castle will only stand if Merlin's blood is mixed with the mortar. After the Soothsayer asks Mab for guidance, she orders him to find Merlin and bring him to Vortigern. Merlin is captured by the king's guards, Vortigern orders the Soothsayer to kill him, but relents when Merlin tells Vortigern of his vision: a red dragon representing Uther defeating the white dragon that represents Vortigern.

Mab persuades the king that he can defeat Uther by sacrificing Nimue to a dragon in the hope that Merlin will break his vow not to use magic. Vortigern is reluctant due to his agreement with Ardent. Frik, disguised as one of Vortigern's guards, falsely claims that Ardent has defected to Uther. Convinced of Ardent's betrayal, Vortigern agrees to Mab's deal and the two become allies. Merlin uses magic to untie himself from a tree and save Nimue, but not before the dragon badly burns her. Merlin brings Nimue to Avalon to recover from her burns. Merlin asks the Lady of the Lake for help, and she gives him the magical sword Excalibur. Merlin warns Uther of Vortigern's intention to attack him in winter instead of spring. Heeding his warning, Uther agrees to meet Vortigern at the battlefield. During the battle, Vortigern kills Ardent and Merlin uses Excalibur to break the ice, causing Vortigern to drown in the freezing water. Afterwards, Merlin gives Excalibur to Uther and he is crowned king.

During a feast celebrating Uther's victory, Mab uses her magic to make Uther become obsessed with Igraine, the wife of Gorlois, Lord of Cornwall. Seeing his emerging madness, Merlin tricks Uther out of Excalibur and plunges it into the Rock of Ages, who promises to keep it until a good man can withdraw it. Uther's mind is plagued by lust for Igraine, and Britain slides back into civil war. Merlin strikes a deal with Uther to let him seduce Igraine in exchange for guardianship of the son born from the union and for Gorlois and his men to be spared. Merlin transforms Uther's appearance into that of Gorlois, fooling everyone in Tintagel Castle except for Igraine's young daughter, Morgan le Fay. After seducing Igraine, Uther has Gorlois and his men slaughtered, deliberately going back on his word to Merlin.

Nine months later, Igraine goes into labor, while Frik, at Mab's behest, convinces Morgan to place a black stone beneath the baby's sheets in his crib. Igraine gives birth to Arthur much to Merlin's relief. Mab confronts Merlin, proclaiming Arthur to be damned, but Merlin vows to raise him in the ways of good and hopes Arthur will help bring about her demise.