Tom Natsworthy, a 15-year-old apprentice Historian at the beginning of the series, he eventually has diverse adventures across the world. Admires head of historians (Valentine) and has a strong sense of curiosity.
Hester Shaw, a fierce young woman with a horrible scar across her face. Seeks revenge on Valentine
Wren Natsworthy, Tom and Hester's daughter who is kidnapped from their home and, as a result, finds herself experiencing the same sort of adventures as her parents had.
Nimrod Pennyroyal, a supposed historian and author who is actually a fraud. He is selfish, narcissistic and cowardly, but has a knack for surviving dangerous experiences, and often shares adventures with the Natsworthy family.
Anna Fang, an Asian pilot and former owner of the Jenny Haniver, she is also a leading agent of the Anti-Traction League. She is killed at the end of Mortal Engines but is resurrected as a Stalker who overthrows the rulers of the League and installs herself as a military dictator.
Shrike, an ancient Stalker who raised Hester after her parents were killed. In the American release of the series he is called Grike.
Theo Ngoni, an African aviator who runs away from his home to join the Green Storm, and later becomes very close to Wren.
Fever Crumb, a member of the Order of Engineers. She is the main character of the prequel series.
Sathya, an Indian Anti-Tractionist and one of the founding members of the Green Storm. Later, after losing her hand to the Stalker Fang, she retires to a hermitage on the slopes of Zhan Shan. Eventually she becomes Fishcake's foster-mother.
Captain Khora, an African soldier of the Anti-Traction League, and captain of the gunship Mokele Mbembe. Later he becomes Air Marshal Khora and commander of the Zagwan Flying Corps.
Chudleigh Pomeroy, a member of the Historian's Guild. He helps Katherine by giving her a place to hide Bevis Pod, and fighting off Crome's Engineers when they attempt to kidnap her. After the destruction of London, he is Lord Mayor of the surviving Londoners but passes away before New London is complete.
Clytie Potts, a member of the Historians' Guild who helps in the fight against the Engineers. After the destruction of London, she takes on the alias of Cruwys Morchard to ferry in supplies to the London survivors.
Gargle, a Lost Boy who (when he was very young), was a member of Caul's Anchorage crew . He later becomes the de facto leader of the Lost Boys, but when he comes to Anchorage-in-Vineland for the Tin Book, he is shot by Hester as she tries to rescue Wren.
Windolene Pye, an old member of Anchorage's Steering Committee who marries Søren Scabious, Anchorage's Engine Master.
Oenone Zero, a Green Storm mechanic who appears in the last two books of the quartet. She plays an important role in creating and maintaining their Stalkers, including Shrike and the Stalker Fang, but she becomes disillusioned with the war after being forced to turn her brother into a Stalker, and plots to assassinate the Stalker Fang.
Thaddeus Valentine, a dashing and handsome Historian often idolised by younger Historians - though his less public image involves murder and thievery as an agent of London. He was killed in the destruction of London by MEDUSA. He is in fact Hester's biological father.
Magnus Crome, the megalomaniacal mayor of London. Killed when it is destroyed.
Katherine Valentine, Thaddeus Valentine's daughter. After uncovering her father's dark secret, she attempts to stop him, with help through Bevis Pod and the Historians guild; however, he accidentally kills her with his sword just before MEDUSA destroys London.
Bevis Pod, a young apprentice Engineer. He works with Katherine to uncover Valentine's plans and falls in love with her. Killed when the 13th Floor Elevator crashes on London's top tier after being shot down by Tom. Estranged son of Dr. Lavinia Childermass.
Chrysler Peavy, the pirate mayor of Tunbridge Wheels. He takes Tom and Hester to the Black Island, expecting Tom (because he is a Londoner) to teach him how to be civilised. He is betrayed and shot by the remainder of his crew shortly before they themselves are killed by the Stalker Shrike.
Nimrod Pennyroyal, Renowned author of adventure books, he pays Tom and Hester to give him a lift to America. Later in the quartet we discover that he lied in all of his books and made the stories up.
Freya Rasmussen, The young margravine of Anchorage, she read Pennyroyal's book about America, and steers Anchorage to it. Only to find it a fraud, she later finds a habitable zone for the city and became static. She is later married with Caul.
Mr. Scabious, chief engineer of Anchorage. He considers Tom similar to his late son, and often tries to help him. He dies sometime before Infernal Devices.
Piotr Masgard, chief of Arkangel's Huntsmen: bands of warriors who capture cities by airship and then steer them into Arkangel's jaws. Actually he is a coward and unused to a fair fight. He is violently killed by Hester during the attack on Anchorage.
Nabisco Shkin, the man behind the Shkin Corporation (a slave dealer in Brighton). He is killed while attempting to escape Brighton during the Green Storm's attack on the city.
Theo Ngoni, a former Green Storm tumbler pilot, now a slave aboard Brighton, he later escapes with Wren at the end of the book. They become more engaged in the other and pursued married with her at the end of the quartet.
Boo-Boo Pennyroyal , the wife of Nimrod Pennyroyal and Mayoress of Brighton. She does little except shop and attend operas, but encourages Wren and Theo's non-existent secret romance.
Mr Plovery , an antiques dealer in Brighton with an expensive elderly mother to look after. He is killed by a Stalker Bird when he tries to steal the Tin Book, however his death is mistakenly attributed to Pennyroyal's security system.
Remora, a Lost Girl and Gargle's girlfriend. She is killed by Hester.
Krill, a Lost Boy captured by Brighton's WOPCART scheme. Hester frees him to create a diversion while rescuing Wren.
Kriegsmarshal Von Kobold, the leader of Marnau, and Wolf Kobold's father. He wants peace for his city and has a soft spot for certain members of the Green Storm.
Wolf Kobold, the German commander of a small harvester suburb called Harrowbarrow. He resents his parents and their high position. He leads Tom and Wren to the wreckage of London on a somewhat false pretext, and escapes with the knowledge of New London, intending to return and devour it with Harrowbarrow. He is killed accidentally by Wren during a sword fight atop his suburb, in which he is impaled and falls under the tracks.
Napster Varley, an aspiring trader who buys Lady Naga and tries to sell her to the Traktionstadtsgesellschaft. He has a wife (bought at an auction) that he frequently beats up; and son, Napster Varley, Jr. He is shot by the hand of his own spouse as Hester and Theo attempt to rescue Lady Naga.
Dr. Lavinia Childermass, an elderly Engineer who survived the MEDUSA incident because she was locked in prison, having rebelled against the insane Magnus Crome. She was head of the Engineer's Magnetic levitation Research Division, and was made Deputy Mayor of the Londoners that survived in the city's wreck. She personally built the Mag-Lev engines that operated New London (known as the Childermass Engines). After the death of Chudleigh Pomeroy, she is denied the mayorship of New London, and then helps Wren and Theo escape the paranoid clutches of the new Lord Mayor, Mr. Garamond. It is revealed that she had a son, but due to Magnus Crome's new laws for the Guild of Engineers, the boy was taken away as a baby. She named him Bevis, alluring to the fact that she was the mother of Bevis Pod, who helped Katherine Valentine investigate MEDUSA in Mortal Engines.
Fever Crumb The central character of the book, she is part human, part scriven mutant and descendant of Auric Godshawk. She is also bisexual, and falls in love with Cluny in the last book.
Dr Crumb, Fever's adoptive father. It is later revealed that he is actually her biological father as well.
Quercus, Land Admiral of the nomadic Movement. After he fights Ted Swiney he becomes mayor of London. At the end it is hinted that he is the great "Quirke" who is revered as a god in the Mortal Engines Quartet.
Charley Shallow, A boy who worked in Ted Swiney's pub until Bagman Creech, a Skinner, came and offered him a job as a Scriven slayer..
Ruan Solent, Kit's son.
Fern Solent, Kit's daughter.
Wavey Godshawk Daughter of Auric Godshawk and Fever's mother, she is the last pure Scriven.
Auric Godshawk Deceased King of the Scriven who placed a computer storing his consciousness into Fever's brain.
Kit Solent, a kind archaeologist who Fever Crumb is sent to work with. He is shot by rioters in London and dies from his wound while fleeing from the city in a hot air balloon. Afterwards he is turned into Shrike.
Ted Swiney, an unpleasant Cockney tavern owner who later becomes mayor of London. During a fight with Quercus he is crushed by a giant barrel.
Bagman Creech, a renowned "skinner" (Scriven killer) from the uprising in London. He is shot and killed by Kit Solent.
Master Wormtimber master of devices. Killed when Godshawk's Head collapses onto him.