This is a list of characters in the Beast Wars franchise, which is part of the larger Transformers franchise from Hasbro. This includes characters appearing in an animated series, comics or video games. This does not include characters only appearing in collector's club or convention-related comics (from 3H or Fun Publications), or toy-only characters. Appearances within the Beast Wars Sourcebook are not counted as appearances within IDW fiction for purposes of this table, as the Beast Wars Sourcebook was an attempt to include all characters from all Beast Wars fiction.

Optimus Primal (voiced by Garry Chalk) is the commander of the Axalon crew, and the main character of both Beast Wars and Beast Machines. His beast mode is a gorilla. Optimus starts off the series as a charismatic and competent leader, but also young and inexperienced. As the series goes on, he proves to be highly competent with a strict form of honor, though he is somewhat irreverent and is perfectly willing to bend the law. A running gag throughout the series is his penchant for stuffy and long speeches, something that Rattrap and even Megatron mock him for. In “Other Voices”, he goes on a risky mission to destroy the Vok Planet Buster. He succeeds, only to be killed thanks to a booby trap rigged by Megatron. However, in "The Coming of the Fuzors", Rhinox implants his spark in a blank protoform, reviving him in a Transmetal body. After Megatron fatally wounded Optimus Prime, threatening to erase the Maximals from existence, Optimus Primal takes his namesake’s spark into his body, transforming him into the highly powerful Optimal Optimus. During the finale, he attacks the Nemesis after it fires on and kills Tigerhawk, before boarding it and battling Megatron. He defeats Megatron, and he and the Maximals tie him to an Autobots shuttle. Before they depart the planet, Optimus memorializes his dead friends and declares the Beast Wars over.

In Beast Machines, Optimus becomes a more spiritual character, seeing visions from and communicating with the Oracle. He slowly becomes fanatical, becoming convinced that he must make Cybertron completely organic, resulting in him and Cheetor coming into conflict multiple times. Optimus is killed in a battle with Tankor and Megatron when he causes a storm of plasma energy. His spirit comes to the realization that he has become a fanatic and that his true purpose is to create a balance between the technological and the organic. After apologizing to his friends, Optimus chooses to remain on Cybertron rather than pass on, and is revived by the Oracle. Optimus then leads his companions on a quest to liberate the sparks Megatron had taken. After several failed attempts, he manipulates Megatron into allowing him to learn the location of the sparks. Optimus and the Maximals seemingly defeat Megatron, only for Megatron to return, leading his drones to extract the sparks of all except Optimus. Optimus battles Megatron, who absorbs the sparks of every Cybertronian and attempts to reformat Cybertron's core. Optimus distracts Megatron and knocks them both into the core, killing them but restoring the sparks to life. Optimus's spirit speaks to Cheetor one last time, before joining with the Matrix.

Cheetor (voiced by Ian Corlett) is an impulsive young rookie whose beast mode is a cheetah. He looks up to his elders but doesn't always follow their orders, and he frequently gets into trouble. He matures throughout the series from a typical teenager to a capable warrior, aided by his mutations into a Transmetal and then a Transmetal II form granting him greater strength.

In Beast Machines, he is promoted to second-in-command after his suspicions about an organic tree being 'dangerous' to the Maximals' techno-organic beast modes prove correct, nearly causing Optimus, Blackarachnia and Rattrap to regress to their beast instincts. For a time Cheetor becomes the Maximals' military leader while Optimus becomes fixated on his new link to the Oracle, but Optimus eventually returns to his role as leader when he gains a better understanding of his mission. In the finale, it is strongly implied that Cheetor will become the new full-time leader after Optimus's death in the final battle.

Rhinox (voiced by Richard Newman) is the tech expert of the Axalon crew, close friend of Optimus, and the second-in-command whose beast mode is a rhinoceros. Rhinox is highly skilled in combat but is highly spiritual and loves nature. He is highly intelligent as well, serving as the Maximal’s resident technician due to his tech-savvy nature. He primarily uses twin chainguns as weapons.

In Beast Machines, Rhinox is captured by Megatron and has his spark used to power the Vehicon general Tankor. Rhinox's personality is brought to the forefront by Optimus, but his time as Tankor had corrupted his personality and caused him to embrace Megatron's plan for a purely technological Cybertron. Rhinox decided that Megatron was unfit to carry out this plan and that he instead should be the one to do so. He began plotting against Megatron, intending to betray him. However, when Rhinox makes his final move and attempts to murder him, Megatron reveals he had programmed his generals to be unable to shoot him. Megatron shuts Rhinox off, and he is killed by plasma energy. Rhinox's spirit later approaches Optimus inside the Matrix, expressing regret for his misguided actions.

Rattrap (voiced by Scott McNeil) is the hacker, saboteur, and demolitions expert whose beast mode is a rat. He is cunning and resourceful, but sarcastic and querulous. Rattrap at first seems to come as a coward, often proclaiming “We’re all gonna die!” whenever he is put in danger. However, he has proven himself to be quite brave, risking his life multiple times for his teammates. He develops an odd cross between a friendship and a rivalry with Dinobot, the two often bickering with each other, albeit sharing a mutual respect. After Dinobot’s betrayal, Rattrap is enraged and loathes him for it, although he forgives Dinobot as he dies of his injuries.