Meriadoc Brandybuck (Westron: Kalimac Brandagamba; usually called Merry) is a Hobbit, a fictional character from J. R. R. Tolkien's Middle-earth legendarium, featured throughout his most famous work, The Lord of the Rings. Merry is described as one of the closest friends of Frodo Baggins, the main protagonist. Merry and his friend and cousin, Pippin, are members of the Company of the Ring. They become separated from the rest of the group and spend much of The Two Towers making their own decisions. By the time of The Return of the King, Merry has enlisted in the army of Rohan as an esquire to King Théoden, in whose service he fights during the War of the Ring. After the war, he returns home, where he and Pippin lead the Scouring of the Shire, ridding it of Saruman's influence.

Commentators have noted that his and Pippin's actions serve to throw light on the characters of the good and bad lords Théoden and Denethor, Steward of Gondor, while their simple humour acts as a foil for the higher romance involving kings and the heroic Aragorn.

Merry appeared in Ralph Bakshi's animated film Lord of the Rings, the animated version of The Return of the King by Rankin/Bass, and in the live action film series by Peter Jackson.

Meriadoc, a hobbit, known as Merry, was the only child of Saradoc Brandybuck, a Master of Buckland, and Esmeralda (née Took), the younger sister of Paladin Took II, making him a cousin to Paladin's son, his friend Pippin. His grandfather Rorimac Brandybuck's sister Primula was the mother of Frodo Baggins, the main protagonist of the book. Merry and Frodo were thus first cousins once removed. Hobbits of the Shire saw Bucklanders as "peculiar, half foreigners as it were"; the Bucklanders were the only hobbits comfortable with boats; and living next to the Old Forest, protected from it only by a high hedge, they locked their doors after dark, unlike hobbits in the Shire.

Merry learned of the One Ring and its power of invisibility before Bilbo Baggins left the Shire. He guarded Bag End after Bilbo's party, protecting Frodo from unwanted guests. Merry was a force behind "the Conspiracy" of Sam, Pippin, Fredegar Bolger and himself to help Frodo. He assembled the company's packs and brought ponies. His shortcut through the Old Forest distanced them from the Black Riders, the Nazgûl, for a time. In the Barrow-downs, he is given his sword, a dagger forged in the kingdom of Arthedain. Arriving at Bree, Merry was not celebrating in the Prancing Pony when Frodo put on the Ring; he was outside taking a solitary walk, and was nearly overcome by a Nazgûl. At Rivendell, he was seen studying maps and plotting their path. Elrond reluctantly admitted him and Pippin to the Company of the Ring.

Halted at the entrance to Moria, Merry asked Gandalf the meaning of the door inscription "Speak, friend, and enter". When Gandalf, having unsuccessfully tried many door-opening spells, discovered the true interpretation, he said "Merry, of all people, was on the right track". At Amon Hen, the Hill of Seeing, the Company hesitated in confusion, and scattered. Merry and Pippin were captured by a band of Saruman's Uruk-hai, despite Boromir's defence. Escaping with Pippin into Fangorn forest, they were rescued by the leader of the Ents, Treebeard, and given an Ent-draught to drink: it made them both grow unnaturally tall for hobbits. Accompanying Treebeard to the Entmoot and later to the wizard Saruman's fortress of Isengard, which the Ents destroyed, they took up residence in a gate-house, meeting King Théoden of Rohan, and were reunited with the Fellowship. Merry swore allegiance to Théoden and became his esquire. Against Théoden's orders, he rode to Gondor with the King's niece Éowyn, who disguised herself as a common soldier. In the Battle of the Pelennor Fields, while the leader of the Nazgûl was preoccupied with Éowyn, Merry stabbed him behind his knee. The Black Captain stumbled, enabling Éowyn to kill him. This fulfilled the prophecy that he would not be killed "by the hand of man", as it was a hobbit and a woman that ended his life. Éomer made Meriadoc a Knight of the Mark for his bravery, and gave him the name Holdwine.

After the War of the Ring, Merry and Pippin returned home as the tallest of hobbits, only to find that Saruman had taken over the Shire. Merry and Pippin roused the hobbits to revolt. During the resulting Scouring of the Shire, Merry commanded the hobbit forces, and killed the leader of Saruman's "ruffians" at the Battle of Bywater. Sometime afterwards, Merry married Estella Bolger. Merry inherited the title Master of Buckland at the start of the Fourth Age. He became a historian of the Shire. At the age of 102, Merry returned to Rohan and Gondor with Pippin; they died in Gondor, and were laid to rest among the Kings of Gondor in Rath Dínen, the street of tombs, then moved to lie next to Aragorn. His son succeeded him as Master of Buckland.

When Merry first appeared in Tolkien's early drafts, his name was Drogo Took. He was later renamed Vigo, and the name Drogo reassigned to Frodo's father. After that, he was renamed Marmaduke, and finally Meriadoc Brandybuck.