gets called "Bell" as a nickname by his younger sister, Octavia. Full name - Bellamy Blake love interest - Clarke, they aren't dating yet Born on The Ark, Bellamy's primary motivation throughout his life is protecting his younger sister, Octavia Blake. He snuck onto the initial dropship bound for Earth disguised as a guard just to keep her safe. On Earth, he emerges as an initial leader of the 100 delinquents, often clashing with co-leader Clarke Griffin as his early style leans self-serving, charismatic, and ruthless in the name of survival. Nonchalant, kind, also can be skeptical but typically believes in what is right for the people he cares for.

full name - John Murphy, often gets called by his last name, "Murphy". He acts as a bully and one of Bellamy Blake’s chief enforcers early on, often showing cruelty and a lack of empathy for others. Sarcastic, skeptical, doesn't trust easily.

full name - Clarke Griffin Intelligent, kind, empathetic, good at being a leader and thinks of everyone's opinions before making a decision, often selfless and still gets misunderstood sometimes when she has to take a hard choice. She arrives on Earth carrying the stigma of a treason charge (for trying to expose the failing oxygen supply on the Ark), earning her the dismissive nickname "Princess" from fellow delinquent Bellamy Blake. Using her medical training from her mother, Dr. Abigail Griffin, Clarke steps up to treat injuries, identify edible plants, and locate safe water sources for the struggling group. She quickly emerges as a de facto leader alongside or in tension with Bellamy, trying to impose order, rules, and logic on a chaotic group of teenagers.

full name - Octavia Blake younger illegal sister of Bellamy Arrested on the Ark simply for being an illegal second child, she spent her early life in total confinement, making her starved for simple experiences and outside air. Upon arriving on Earth, she embraces her first taste of liberty with joy and impulsiveness, eager to strip away the rules of her past. a sheltered, rebellious teenager who spent her whole life hidden under a floor into a fiercely independent young woman tasting freedom for the first time.

full name - Monty Green bestfriends with Jasper Arrested on the Ark as a juvenile for stealing hydroponic garden herbs, which reflects his deep-rooted expertise in botany and engineering. Serves as Jasper's loyal anchor; much of Monty's early motivation revolves around protecting and looking out for his quirky best friend, especially after Jasper is speared by Grounders early on.

full name - Finn Collins Finn was sent to Earth because he took the blame for an illegal spacewalk that wasted precious oxygen on the Ark, earning him his famous nickname. In reality, the idea was his, but his girlfriend Raven Reyes actually did the spacewalk. Unlike the aggressive and power-hungry early version of Bellamy Blake, Finn initially pushes for peaceful coexistence with the Grounders and tries to find non-violent solutions to their survival challenges. He quickly forms a deep romantic connection with Clarke Griffin, but their relationship hits a major hurdle when Raven manages to arrive on Earth via a escape pod, revealing that Finn had a girlfriend back in space whom he hadn't mentioned to Clarke.

full name - Jasper Jordan bestfriend - Monty He grew up on the Ark space station in the agricultural section and was sent to juvenile detention alongside his best friend, Monty Green, for stealing herbs. optimistic, awkward, and enthusiastic teenager before turning braver and more hardened after enduring severe trauma. In the pilot episode, he is brutally speared in the chest by a Grounder while scouting Mount Weather. He spends a large portion of the early episodes recovering from this near-fatal wound.

Full name - Raven Reyes She grew up on Mecha Station with an absentee mother and worked as a skilled spacewalker She fixes an old escape pod to travel down to the surface, carrying vital equipment and radio parts to reconnect the teens with the Ark. She comes to Earth primarily to find her boyfriend, Finn Collins, though their relationship fractures after she discovers his growing feelings for Clarke Griffin.

She is the powerful Commander (Heda) of the allied Grounder clans. During the first season, the Grounders are mentioned and fought, but their leader—the Commander—is only referred to abstractly rather than shown on screen.