For the Term of His Natural Life is a story written by Marcus Clarke and published in The Australian Journal between 1870 and 1872 (as His Natural Life). It was published as a novel in 1874 and is the best known novelisation of life as a convict in early Australian history. At times relying on seemingly implausible coincidences, the story follows the fortunes of Rufus Dawes, a young man transported for a murder that he did not commit. The book clearly conveys the harsh and inhumane treatment meted out to the convicts, some of whom were transported for relatively minor crimes, and graphically describes the conditions the convicts experienced. The novel was based on research by the author as well as a visit to the penal settlement of Port Arthur, Tasmania.

Structurally, For the Term of His Natural Life is made up of a series of semi-fictionalised accounts of actual events during the convict era, loosely bound together with the tragic story of its hero. Most of the incidents and many of the individual characters are easily identifiable from historical sources including Marcus Clarke's own non-fiction work Old Tales of a Young Country.

Typically of Victorian-era convict novels, Rufus Dawes is a wrongfully convicted gentleman; contemporary readers would have considered an actual murderer an inappropriate hero for a work of popular fiction.

The story starts with a prologue, telling the tale of young British aristocrat Richard Devine, who is the son of a shipbuilding magnate, Sir Richard Devine. In an incident of domestic violence, Richard's mother reveals to Sir Richard that his son was fathered by another man, Lord Bellasis. Sir Richard proceeds to threaten the mother's reputation if Richard does not leave and never come back. He leaves him to pack for a while, claiming that he will fetch his lawyer to alter his will so that Richard receives no inheritance. When Richard leaves, he comes across a murder scene: his biological father, Lord Bellasis has been murdered, and Richard witnesses Sir Richard walking away from the scene of the crime. The police come and lock up Richard, who now gives his name as Rufus Dawes (which is used for the remainder of the book), for the murder of Lord Bellasis. Additionally, Sir Richard returns home and dies straight away, possibly of a heart-attack, without altering his will. Rufus Dawes/Richard Devine never finds this out. Rufus is found not guilty of the murder but guilty of the robbery of the corpse and sentenced to transportation to the penal colony of Australia.

In 1827, Dawes is shipped to Van Diemen's Land on the Malabar, which also carries Captain Vickers, who is to become the new commander of the penal settlement at Macquarie Harbour, his wife Julia and child Sylvia, Julia's maid, one Sarah Purfoy and Lieutenant Maurice Frere, Richard Devine's cousin, son of Sir Richard's sister, who would have inherited the fortune in Richard's place. It turns out that Sarah is on the vessel only to free her lover, John Rex. She organises a mutiny with the help of three other men: Gabbett, James "Jemmy" Vetch or "the Crow" and a man nicknamed "the moocher", while John Rex is in hospital with the fever. One night, a burning vessel is sighted and discovered to be the Hydaspes; the ship on which Richard Devine is supposed to have sailed. The crew cannot be found. The following day, Dawes overhears the plans of the mutineers, but is taken to the hospital sick with the fever shortly afterwards. He manages to warn Captain Vickers and Doctor Pine about the plans. Sarah gets the Captain drunk and Frere otherwise busy but does not know about Vickers clandestinely doubling the guard. The mutiny is, therefore, unsuccessful, but Jemmy Vetch, who has understood that only Dawes could have betrayed them, gets his revenge by claiming that Dawes was the ring leader of the mutiny. Dawes is found guilty and receives a second life sentence.

In 1833, at Macquarie Harbour, Maurice Frere has come to deliver to Captain Vickers the news that the settlement at Macquarie Harbour is to be abandoned and the convicts to be moved to Port Arthur. He also attempts to befriend Sylvia, but the child resents him ever since witnessing his treatment of the convicts (especially that of Dawes, who went to the quarterdeck to return her ball). Rufus Dawes has been the victim of several assassination attempts at the convicts' hands, but has also attempted escape twice and has a long record of bad conduct and punishments. At the moment of Frere's arrival, he is in solitary confinement on Grummet rock, a small island before the coast. Dawes has managed to recognise Frere at the harbour and now, seeing the preparations for the abandonment of the settlement, mistakenly assumes that Frere has taken command. Rather than suffer Frere's treatment upon his return, he attempts to drown himself.

Meanwhile, it has been decided that Vickers should sail with the convicts and Frere follow with the brig Osprey with Mrs. Vickers and Sylvia, the pilot, five soldiers and ten convicts. Among the convicts is John Rex, who has again plans for mutiny. The convicts succeed in taking the boat, killing two soldiers, wounding one, and marooning him with the Vickers, the pilot and Frere. The pilot and the wounded man die shortly afterwards. One night, a man reaches their makeshift camp. It is Rufus Dawes, who has managed to swim to the settlement only to find it deserted. Although initially wary of him, the little community soon accepts Dawes, especially since he knows many ways to make their life more agreeable. Sylvia takes to him and Dawes soon does everything to please her, despite Frere's jealous attempts to win Sylvia's affection. It is also Dawes, who, after Sylvia mentioned the coracles of the Ancient Britons, plans and succeeds in building a boat out of saplings and goat hide. Although Frere promises Dawes a pardon, he nevertheless does not stop treating him like an inferior, at one point upsetting Dawes so much that he considers leaving on his own. Only Sylvia's writing in the sand, "Good Mr. Dawes", stops him. Through a hazard, Frere tells Dawes of the fate of his cousin and how narrowly he missed inheriting the Devine fortune. Dawes had not known about Sir Richard's death. Finally, they set to sea with Mrs. Vickers gravely ill and Sylvia soon also sick. After some time they are found by an American vessel at which point Frere takes the rudder of the boat and Sylvia in his arms.

By 1838, in Port Arthur, Mrs. Vickers has died. Sylvia has lost all her memories of the incident at Macquarie Harbour and knows only what she has been told about it. She is now a young woman of sixteen and engaged to Captain Maurice Frere, who has told the story of the mutiny in his own way: making himself the hero and claiming that Dawes attempted to murder all three of them. News arrives that the surviving mutineers of the Osprey have been captured and are to be tried at Port Arthur. Sarah Purfoy calls on Frere and begs him to speak in Rex's favour, saying that he left them food and tools. She threatens to expose Frere's previous affairs to Sylvia. Frere consents to her demands. Rufus Dawes is also brought down from Hobart to identify the captured men. At the trial, he sees Sylvia again and realises that she is alive: he had been informed of her death. He tries to speak his case but is not allowed to. The mutineers get away with life sentences.