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.

A Belter detective working for Star Helix Security on Ceres Station. Burnt out, underpaid, and living in his hat. Assigned to find a missing girl named Julie Mao, he becomes obsessed with the case long after it stops being a job. The investigation costs him everything and leads him to the heart of the greatest conspiracy in 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.

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.

An Earther and security officer on Ceres station, partnered with Josephus Miller. His off-world background makes him an outsider in the predominantly Belter station.

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.

Daughter of industrialist Jules-Pierre Mao and crew member of the Scopuli. A young woman from a wealthy Earth family who rejected her privileged background to join the OPA and fight for Belter rights.

A Protogen scientist and one of the architects of the protomolecule experiments on Eros. Dresden is coldly rational, viewing the deaths of thousands as acceptable losses in the pursuit of understanding the alien technology.

The captain of the ice hauler Canterbury. McDowell is a pragmatic, experienced captain who tries to keep his crew safe in the Belt's dangerous shipping lanes.

Miller's boss at Star Helix Security on Ceres station. Shaddid assigns Miller the Julie Mao case and grows increasingly frustrated with his obsessive pursuit of it.

A young Belter who helps Miller on Eros. Diogo is brash and enthusiastic, representing the younger generation of Belters who see the conflict as an opportunity for OPA glory.

A Marine officer commanding the OPA boarding team that accompanies the crew. Kelly is professional, disciplined, and loyal to Fred Johnson's mission.

An Earther encountered during the events of the Expanse series.

The medic aboard the Canterbury and later the Knight. Shed is nervous, compassionate, and out of his depth in the escalating conflict that follows the Canterbury's destruction.