Main characters
Cassiopeia "Cassie" Marie Sullivan - the main protagonist of the series. Her namesake is the constellation Cassiopeia. Both of her parents died in the first four waves. Her younger brother Sammy is taken by The Others to a "training camp" called Camp Haven, formerly, Wright-Patterson AFB. She is seventeen years old and is described as a short, strawberry-blonde girl with average features.
Evan Walker - a farm boy from rural Ohio. All of his family and girlfriend were killed in the Third Wave by the Red Death. Earlier in his life at a carnival, he meets Grace, who is the only person he finds to be like him, an Other. He saves Cassie after she is shot by an Other sniper, the "Silencer". Cassie soon finds out that Evan is actually an Other and not truly human. He is described as being a tall boy, at least eighteen or nineteen years old, being very muscular with chocolate-brown hair. Cassie also notes his soft hands. He develops strong feelings for Cassie, and so does she. Though, these feelings are strained when Cassie learns that Evan is an Other. Evan is rescued by Grace, who tries to seduce him, but, after they are attacked and Grace is wounded, he makes his way to Cassie. Grace, however, follows him there. A confrontation ensues, after which Poundcake blows up the hotel after Evan was left behind in the hotel, and it is not clear if Evan survives. However, at the end of The Infinite Sea, he emerges from the woods to find Cassie.
Benjamin "Ben" Thomas Parish or "Zombie" - the varsity quarterback of the football team at Cassie's school. Cassie secretly was in love with him. His family was killed during the first four waves by a group of psychotic looters. He is crushed by the fact that he ran while his baby sister was killed. He keeps a locket with a photo of her. He becomes a member of Camp Haven's makeshift army, not knowing that they are The Others (though he eventually finds out), taking the nickname "Zombie". After one of his squadmates goes crazy, or "Dorothy", Private Ringer replaces him. He obsesses with getting her to smile. Cassie describes him as overall gorgeous.
Marika "Ringer" - a member of Squad 53. Her father was an Atheist and a chess player. He taught her how to play. Marika's father was usually drunk. Her father is infected with the Red Death and dies of the disease. Marika wandered through the wilderness before forcefully being recruited into Camp Haven's army, where she took the nickname "Ringer". She is a replacement after Private Tank of Squad 53 went crazy, "Dorothy", and pulled a gun on his squad. Zombie is obsessed with getting Ringer to smile. On their first patrol, she and Zombie find that Camp Haven's officials are actually The Others. She is described as having glossy black hair and mild Asian features. In The Infinite Sea, she grows closer to Private Teacup, and, after being captured, grows feelings for a recruit named Razor.
Sammy "Nugget" Sullivan - Cassie's five-year-old little brother. At his refugee camp, he boards a bus from Camp Haven and is recruited into its army, unbeknownst to his father's death. He joins Squad 53 and friends Zombie deeply. Sammy is not allowed to go on his squad's patrol due to his age. (We later find out the purpose of kids his age at Camp Haven in The Infinite Sea.) Zombie, Cassie, and Evan unite after Commander Vosch attempts to kill Sammy. Evan destroys the base, though it is not clear whether he survives or not, and Cassie, Sam and Ben escape.
Secondary characters
Lieutenant Colonel Alexander Vosch - The main antagonist though the trilogy. He leads the 5th wave bases and Silencers stationed across the world. Throughout the books he is steadily sadistic and cruel. First introduced by killing Cassie's father and gathering her brother Sam into a yellow school bus under the guise of safe keeping. Followed by brainwashing Ben into submitting to a cruel military-style training at Camp Haven. He later destroys Camp Haven, and kills thousands of children in the process. Regularly the reader is reminded of Vosch's hatred, and deep understanding of humanity. He rigs carbon-monoxide bombs into young children's throats to sew mistrust in survivors. He takes memories from the Wonderland program to make himself more trustworthy. One example is mimicking Ringer's father during a chess game to weaken her resolve. He later "enhances" Ringer (Marika) with alien technology called The 12th System, a piece of Other technology. Then offers her a place in the existential Wonderland the "other" survive in.
Grace - a Silencer like Evan, programmed by the 12th System to believe she is a part of the immortal alien "Others" taking over. They befriended each other before the waves began. Grace saves Evan after finding him severely wounded in an escape pod. Unknowingly harboring a tractor to "their kind" after he destroys Camp Haven. The night after one of her hunts, she tries to seduce Evan, but he attacks her and renders her unconscious. Believing her to be dead, Evan heads back to the hotel Cassie's group has taken refuge in, which they had nicknamed "The Walker Hotel". She watches him get slower, the 12th systems breaking down in his body. Waits for him to get inside, get settled. And silently starts her pillage. Cassie's group where she then attacks them. After this violent confrontation, Private Poundcake, now mortally wounded, goes back to the hotel to retrieve the bomb dropped by Sammy and detonates it an arms-length away from Grace, killing both of them.
Dumbo - the twelve year old medical officer in Squad 53. One of his most prominent features is his extraordinarily large ears, like his namesake. He's known for his loyalty, risking himself for the other characters many times over throughout the series. Traveling through Urbana on a hopeless mission to save Teacup and Ringer, he dives into Zombie at the last second and takes a bullet to the back. Unable to stay Zombie leaves Dumbo with the promise to return with Ringer and Teacup. When he returns he finds Dumbo has crawled ten blocks away in delirium, looking for Zombie.
Allison "Teacup" or "Cup" - a seven-year-old member of Squad 53. She is described as "the meanest seven-year-old you've ever seen" by Zombie. Teacup grows close to Ringer as the only other female in Squad 53, especially after the destruction of Camp Haven. She is shot by Ringer who mistakes her for an Other. Ringer surrenders to Vosch knowing it is the only way to save Teacup's life, and Vosch uses Teacup as leverage against Ringer. Teacup is killed by Razor so Vosch will have no more leverage against her.
Poundcake - a chubby member of Squad 53 who is mostly silent. His mother was killed by the Red Death. While he was on a supply run, he returned to find his brother gone. On the supply run, he found only a sweet treat, his namesake, as his drill sergeant thought he was "so sweet". He sacrificed himself to save the others of his group by detonating a bomb rigged to detonate on high concentrations of carbon dioxide in close proximity to Grace, a Silencer targeting the group.
Megan - a seven-year-old girl rescued and taken to Camp Haven. She meets and befriends Sammy on the bus they ride. Megan is, along with many other kids her age that are part of the Fifth Wave, rigged with a carbon dioxide-bomb. She is dropped off near Cassie's group's hideout. Evan and Cassie manage to get the bomb out of her, for which they plan to use to attack the others, though Poundcake ends up detonating it to save the others from Grace. She inevitably lives on, independent and untrusting of any character in the books.
Flintstone "Flint" - a boy around Ben and Cassie's age. He is the former leader of Squad 53, until his drill sergeant, Reznik, replaced him with Zombie. In disbelief that Camp Haven could be a coup, he accidentally kills himself by taking the tracking devices and detonating his own kill-switch.
Tank - a young boy in Squad 53. He goes "Dorothy" (crazy) and is replaced by Ringer. Zombie and Dumbo discover him dead in the P&D Hangar (Processing and Disposal).
Kenny "Oompa" - an eight-or-nine-year-old boy on Squad 53. He is killed by grenade shrapnel on the squad's first patrol.
Razor - Alex a recruit at the northern base where Ringer was captured. He is ordered to bring her food three times a day after she's injected with the 12th system. Despite being ordered not to speak to her he rambles during their time together: his favorite things in life, before and after the others. Prayer circles. His grandmother nippy purse dog he prayed would not die because his grandmother told him to. Even though he hated the dog, he was upset when it died. He introduces a game of his own creation: Chaseball (baseball played on a chessboard using a quarter). He orchestrates her and Teacup's escape from the military base though secrets codes traced on board. After jumping from a Blackhawk manned by Lieutenant Bobband surviving, the two kiss. But Ringers 12th includes a CPU attached to her brain that interprets physiological biofeedback. She knew immediately something was wrong. She takes his gun and knocks him out, then finds Vosch inside of the hospital Teacups was supposed to be hiding in. After fighting with Vosch, Ringer is left to heal in an abandoned hospital with Razor assigned to watch her. They are tasked to rid hundreds of dead bodies. He and Ringer attempt to reconcile, her talking much more now, finding she misses the talkative nature he had taken in the military base. By the end of the week they sleep together. He does not have to convince her not to go back to the base: Teacup is there and Razor knows that is Ringer's only weakness. When they return to the base, he shoots Teacup so that Vosch will have no leverage over Ringer. He in turn is shot and killed himself by 5th Wave soldiers.
Lieutenant Bob - Was forced to commandeer a Black Hawk helicopter and escort Ringer, Teacup, and Razor away from Vosch's base. She made him jump out and then crashed it. As if once wasn't enough, she later forced him to fly another Black Hawk back into the base and then blew it up.
