John Rackham (December 21, 1682 – November 18, 1720 in Jamaica), also known as Calico Jack, (often spelled Rackam or Rackum in contemporary documentation), was an English pirate captain during the early 18th century. His nickname was derived from the calico clothing he wore.

John Rackham is most remembered for two things: his Jolly Roger, featuring a skull and crossed cutlasses, which helped to popularize the design and associate it in popular culture with piracy; and employing the two notorious female pirates of the Golden Age of Piracy - Anne Bonny and Mary Read - in his crew.

Rackham originally sailed under Charles Vane, an English pirate captain. In 1718, Vane engaged a vessel which turned out to be a French warship and was forced to retreat. Vane's crew, led by Rackham (who was the ship's quartermaster) voted to remove him as captain on the grounds of cowardice; Rackham was installed as captain in his place.

He made a career of plundering small vessels close to shore, which proved his undoing as he cruised Jamaica in the autumn of 1720. He captured numerous small fishing vessels, terrorizing fishermen and women along the northern coastline before coming across a small vessel filled with other English pirates. The nine armed men were invited aboard, but were almost immediately under attack by an armed sloop sent out by Governor Nicholas Lawes.

Rackham and his crew were captured October 1720 by Captain Jonathan Barnet. Rackham and the male members of the crew were tried and convicted in St. Jago de la Vega (Spanish Town), Jamaica, November 16-17, 1720. Rackham was hanged at Gallows-Point in Port Royal on November 18, 1720. Rackham's body was then tarred, hanged in a cage, and gibbeted on display on a very small islet (first known as Plumb-point) at a main entrance to Port Royal, Jamaica as a warning to other pirates (now known as Rackham's Cay).

The gibbeting is referenced in the Disney film Pirates of the Caribbean: The Curse of the Black Pearl, in which several pirates are hung from an open caveface in the film rendition of Port Royal. Calico Jack's crossed cutlass Jolly Roger was used in Pirates of the Caribbean: The Curse of the Black Pearl and Pirates of the Caribbean: At World's End as Hector Barbossa's pirate flag. It was also used for Geena Davis' flag in "Cutthroat Island."