Pilot of the Rocinante and former MCRN officer. A Martian with a warm, garrulous personality that masks genuine melancholy about his failed family life. One of the finest pilots in human space, with an instinctive feel for orbital mechanics and ship handling.

Mechanic and general muscle aboard the Rocinante. A man who grew up in the worst conditions Baltimore had to offer and emerged without the capacity for moral judgment most people take for granted - he outsources that function to people he trusts. Straightforwardly violent when necessary, and deeply loyal to those he considers his people.

Former XO of the ice freighter Canterbury who becomes captain of the salvaged Martian gunship Rocinante after witnessing the destruction of his ship. A relentless idealist with a compulsion to broadcast the truth regardless of the political consequences, Holden repeatedly finds himself at the centre of events that define the course of human history.

Chief engineer and executive officer of the Rocinante. A Belter of exceptional intelligence and technical skill who carries a painful past involving the Free Navy. The moral conscience of the crew, she is also one of the most capable engineers in the solar system.

Charismatic and ruthless leader of the Free Navy, a radical Belter faction. Responsible for the asteroid strike on Earth that kills billions. A man of genuine political grievance and monstrous methods, whose belief in his own vision is absolute and whose love for his son is the only thing that complicates his certainty.

A charismatic and politically astute OPA faction leader based on Ceres station. A Belter nationalist who operates in the grey area between diplomacy and coercion to advance the interests of the Belt.

A Methodist minister and activist from Earth. A compassionate and principled woman who becomes involved in events aboard the Behemoth as humanity faces the unknown beyond the Ring.

Martian marine gunnery sergeant who witnesses something on Ganymede that her government wants buried. One of the most physically formidable characters in the series, she is also one of its most principled - a soldier who cannot stop asking whether the orders she follows are worth following.

UN Deputy Undersecretary of Executive Administration and one of the most powerful politicians on Earth. Foul-mouthed, brilliant, and utterly clear-eyed about how power works. She plays the long game better than almost anyone in the solar system and genuinely cares about the billions of people whose lives depend on her getting it right.

Daughter of the magnate Jules-Pierre Mao, who frames Holden for a terrorist attack in a misguided attempt to restore her family's honour. After her imprisonment she joins the Rocinante crew, carrying significant guilt and a body modified for violence she is trying to leave behind.

Son of Marco Inaros and Naomi Nagata. A teenager who has grown up entirely within the Free Navy and his father's ideology, and who must find his own identity in its shadow. One of the most psychologically complex characters in the later books.

Former UN Marine colonel who became the most wanted man in the Belt after Anderson Station, and then - through a long process of reckoning with what he had done - became the most important non-Belter leader in the OPA. A man trying to build something better out of the wreckage of his own history.

A Belter officer who serves as executive officer aboard the Behemoth. A skilled and ambitious naval officer with shifting loyalties in the fractured political landscape of the Belt.

Documentary filmmaker and journalist who first joins the Rocinante crew for the Ring expedition, using Freedom of Journalism Act protections. Later operates Radio Free Slow Zone broadcasts from the Behemoth during the crisis inside the ring space.

Chief botanist of the RMD-Southern soy farm project on Ganymede, and father of Mei Meng. A gentle, methodical scientist thrust into a desperate search for his missing daughter. His expertise in botany and the slow logic of growing things sits in sharp contrast to the violence of the world he is forced to navigate.

A Belter and veteran technician on Medina Station. A member of the OPA who helped install the station's defence network.

A technician stationed on Medina Station who works on the installation and maintenance of the station's defence systems.

A crew member aboard the Rocinante during the later books of The Expanse series.

An OPA technician on Medina Station who works for the Free Navy. She grew up on Callisto and helped install the rail gun defence network on the ring station.

A Belter technician serving with the Free Navy on Medina Station. He grew up on Ceres and helped install the rail gun defence network on the ring station.