The story is written as a first person narrative from the perspective of 15-year-old Ralph Rover, one of three boys shipwrecked on the coral reef of a large but uninhabited Polynesian island.
Ralph tells the story retrospectively, looking back on his boyhood adventure: "I was a boy when I went through the wonderful adventures herein set down.
With the memory of my boyish feelings strong upon me, I present my book especially to boys, in the earnest hope that they may derive valuable information, much pleasure, great profit, and unbounded amusement from its pages."

The account starts briskly; only four pages are devoted to Ralph's early life and a further fourteen to his voyage to the Pacific Ocean on board the Arrow.
He and his two companions – 18-year-old Jack Martin and 13-year-old Peterkin Gay – are the sole survivors of the shipwreck.
The narrative is in two parts.
The first describes how the boys feed themselves, what they drink, the clothing and shelter they fashion, and how they cope with having to rely on their own resources.
The second half of the novel is more action-packed, featuring conflicts with pirates, fighting between the native Polynesians, and the conversion efforts of Christian missionaries.

Fruit, fish and wild pigs provide plentiful food, and at first the boys' life on the island is idyllic.
They build a shelter and construct a small boat using their only possessions: a broken telescope, an iron-bound oar, and a small axe.
Their first contact with other humans comes after several months when they observe two large outrigger canoes in the distance, one pursued by the other.
The two groups of Polynesians disembark on the beach and engage in battle; the victors take fifteen prisoners and kill and eat one immediately.
But when they threaten to kill one of the three women captured, along with two children, the boys intervene to defeat the pursuers, earning them the gratitude of the chief, Tararo.
The next morning they prevent another act of cannibalism.
The natives leave, and the boys are alone once more.

More unwelcome visitors then arrive in the shape of British pirates, who make a living by trading or stealing sandalwood.
The three boys hide in a cave, but Ralph is captured when he ventures out to see if the intruders have left and is taken on board the pirate schooner.
He strikes up a friendship with one of the crew, Bloody Bill, and when the ship calls at the island of Emo to trade for more wood Ralph experiences many facets of the island's culture: the popular sport of surfing, the sacrificing of babies to eel gods, rape, and cannibalism.

Rising tensions result in the inhabitants attacking the pirates, leaving only Ralph and Bloody Bill alive.
The pair succeed in making their escape in the schooner, but Bill is mortally wounded.
He makes a death-bed repentance for his evil life, leaving Ralph to sail back to the Coral Island alone, where he is reunited with his friends.

The three boys sail to the island of Mango, where a missionary has converted some of the population to Christianity.
There they once again meet Tararo, whose daughter Avatea wishes to become a Christian against her father's wishes.
The boys attempt to take Avatea in a small boat to a nearby island the chief of which has been converted, but en route they are overtaken by one of Tararo's war canoes and taken prisoner.
They are released a month later after the arrival of another missionary, and Tararo's conversion to Christianity.
The "false gods" of Mango are consigned to the flames, and the boys set sail for home, older and wiser.
They return as adults for another adventure in Ballantyne's 1861 novel The Gorilla Hunters, a sequel to The Coral Island.
The story is written as a first person narrative from the perspective of 15-year-old Ralph Rover, one of three boys shipwrecked on the coral reef of a large but uninhabited Polynesian island. Ralph tells the story retrospectively, looking back on his boyhood adventure: "I was a boy when I went through the wonderful adventures herein set down. With the memory of my boyish feelings strong upon me, I present my book especially to boys, in the earnest hope that they may derive valuable information, much pleasure, great profit, and unbounded amusement from its pages."
The account starts briskly; only four pages are devoted to Ralph's early life and a further fourteen to his voyage to the Pacific Ocean on board the Arrow. He and his two companions – 18-year-old Jack Martin and 13-year-old Peterkin Gay – are the sole survivors of the shipwreck. The narrative is in two parts. The first describes how the boys feed themselves, what they drink, the clothing and shelter they fashion, and how they cope with having to rely on their own resources. The second half of the novel is more action-packed, featuring conflicts with pirates, fighting between the native Polynesians, and the conversion efforts of Christian missionaries.
Fruit, fish and wild pigs provide plentiful food, and at first the boys' life on the island is idyllic. They build a shelter and construct a small boat using their only possessions: a broken telescope, an iron-bound oar, and a small axe. Their first contact with other humans comes after several months when they observe two large outrigger canoes in the distance, one pursued by the other. The two groups of Polynesians disembark on the beach and engage in battle; the victors take fifteen prisoners and kill and eat one immediately. But when they threaten to kill one of the three women captured, along with two children, the boys intervene to defeat the pursuers, earning them the gratitude of the chief, Tararo. The next morning they prevent another act of cannibalism. The natives leave, and the boys are alone once more.
More unwelcome visitors then arrive in the shape of British pirates, who make a living by trading or stealing sandalwood. The three boys hide in a cave, but Ralph is captured when he ventures out to see if the intruders have left and is taken on board the pirate schooner. He strikes up a friendship with one of the crew, Bloody Bill, and when the ship calls at the island of Emo to trade for more wood Ralph experiences many facets of the island's culture: the popular sport of surfing, the sacrificing of babies to eel gods, rape, and cannibalism.
Rising tensions result in the inhabitants attacking the pirates, leaving only Ralph and Bloody Bill alive. The pair succeed in making their escape in the schooner, but Bill is mortally wounded. He makes a death-bed repentance for his evil life, leaving Ralph to sail back to the Coral Island alone, where he is reunited with his friends.
The three boys sail to the island of Mango, where a missionary has converted some of the population to Christianity. There they once again meet Tararo, whose daughter Avatea wishes to become a Christian against her father's wishes. The boys attempt to take Avatea in a small boat to a nearby island the chief of which has been converted, but en route they are overtaken by one of Tararo's war canoes and taken prisoner. They are released a month later after the arrival of another missionary, and Tararo's conversion to Christianity. The "false gods" of Mango are consigned to the flames, and the boys set sail for home, older and wiser. They return as adults for another adventure in Ballantyne's 1861 novel The Gorilla Hunters, a sequel to The Coral Island.
The Coral Island