This is a list of the Transformers: The Defenders episodes seasons 1-3.
- Beginnings Part 1 The Autobots and Decepticons crash land on Earth. 7,000 years later, a boy named Andrew discovers the Autobots. The Decepticons attack Phoenix, Arizona. Then the Autobots came to fight the Decepticons. Megatron holds Andrew up and if Optimus made a move, then Andrew will die...
- Beginnings Part 2 The Autobots had to surrender for Andrew's safety. The battle still continues in Phoenix. Optimus Prime fights Megatron. The Decepticons retreat when Optimus's tank transforms into a battle station. Optimus says that Earth will be protected no matter the cost.
- Desert Storm The Decepticons plan to burn the desert into flames. The Autobots fight the Decepticons. Megatron burns the desert. Optimus tries to find a water source at a nearby fire station.
- Fighting for What's Right Andrew tries to tell his friends about the Transformers, but nobody believed him. Megatron sends Starscream to capture the boy. When the boy gets captured, Optimus sends Roadbuster and Skid-Z. The two fight Megatron and Starscream, but they ended up wounded. Optimus and Ratchet comes and Optimus fights Megatron and Starscream while Ratchet repairs Skid-Z and Roadbuster. Megatron surrenders and let Optimus take Andrew.
- Ultimate Spy Mirage, an Autobot spy encounters the Decepticons in an industrial site. Optimus Prime and the others are creating a space bridge until Ratchet finds out that their old friend Mirage is in trouble. The Autobots fight the Decepticons. Megatron retreats with the other Decepticons. Mirage says that he couldn't join with the team. So he scans a race car and drives out of the factory.
- Fire On the Mountain Optimus Prime and Roadbuster goes to a neuclear site to fight Starcream and Roller Force. Megatron, which is on the mountain next to the neuclear site, he puts dentonators at the peak. The mountain explodes, and Optimus uses his photon blasters to shoot Megatron, but misses. A landslide heads toward to the site, and Optimus uses himself to block the boulders.
- Virus Ratchet gets a computer virus on his computer caused by a Decepticon. Ratchet invents an Auto-Ship to blow up the virus. As Ratchet controls the Auto-Ship, Optimus, Roadbuster, and Skid-Z attaxk Megatron and Starscream at a construction site.
- Black World Roller Force and Ramulus uses Energon to create a cannon that malfunctions when the try to shoot. Megatron uses Darkness Power, used by Liege Maximo to enter the two into a dark void with ancient Autobot enemies.
- Sea Change The Autobots meet a new Autobot, Airazor at the Indian Ocean. Megatron creates an underwater fort to block submarines, boats, or seaplanes from trespassing. Unfortunately, Airazor gets caught since her second mode is a seaplane.
- Secrets of the Brigadoon Mirage goes into another dimensional world after fighting Divebomb. Mirage enters into a peaceful place. When Megatron and his forces enter the new world, the sacred obelisk gains power to destroy chaos.
- The Golden Lagoon Mirage tells Optimus about the Brigadoon, but Optimus claims it's an old Cybertronian legend. Mirage returns to the Brigadoon. After the obelsik got destroyed in the last episode, what was left was a golden lagoon. Mirage enters it and finds himself covered in gold. When he enters Earth, the humans go after him for money.
- Death's Head Part 1 A human scientist discovers a gigantic body at the Stonehenge. He takes it to his lab and the other scientists got tools to open up the body. Before they could cut him, the body returns to life saying,"I am Death's Head!" and destroys the entire lab.
- Death's Head Part 2 The Autobots had to stop Death's Head before he destroys anything else. Death's Head recognizes Optimus Prime as an "enemy that should have been extinguished a long time ago." So he attack Optimus and wounds him to death. The other Autobots have to stop him before Optimus dies.
The Season 1 DVD has a short story called "Future of Cybertron" after the last episode.
- Death's Head Part 3 Death's Head wounds Optimus Prime. Mirage has to use his cloaking to get around Death's Head while the other attack him by a cliff. Ratchet takes Optimus Prime back to base to repair him.
- Revenge Megatron finds out that the Autobots blew up Death's Head. Shockwave and Jetfire fights in space which makes them go on Earth. Megatron is proud to see his Decepticon scientist alive.
- An Underground Discovery Optimus and Ratchet find the body of Ultra Magnus underground. The Autobots resurrect him and Ultra Magnus becomes alive. mirage helps him scan a vehicle. The two of them don't know that the Decepticons are tracking them down.
- Rodimus Rodimus II comes to Earth and the Decepticons try to convince him to join the Decepticons. The Autobots attack the Decepticons, fighting for Rodimus.
- Racing for Demolishing Roadhandler will be at the World Championship against other monster trucks until the Decepticons have to come and fight him.
- Operation: Space Bridge The Autobots are almost finished with the space bridge, but they have to watch for Decepticons. Jetfire went to a junkyard and finds Ramulus scrounging in it.
- Death Of A Leader Megatron wants to fight Optimus face to face at a grassland in Africa. The other Autobots try to stop Optimus from going. Megatron and Optimus starts the fight to determine who will win.
- Bighorn Prime Bighorn Prime searches for Ultra Energon. Meanwhile the Autobots fight Soundwave at a night club.
- Autobot X The Decepticons create an Autobot spy. Unfortunately, they can't seem to control the robot.
- Skydive's Return Skydive, a former general of the Autobot Military Team, comes to Earth in a search for Optimus Prime. Then Ramjet comes looking for Skydive.
- Power of the Vok Ratchet finds out that Rodimus the Second has powers of the Vok when they fight the Decepticons. Rodimus even claims he knows about the Brigadoon, a world created by the Vok.
- The Return of Optimus Prime Megatron meets a long lost Decepticon soldier, Darkwing. When his new comrade attacks the Autobots, a loss comes to help.
- The Fuzors Torca and Sky Shadow enter Earth to find their leaders. Bighorn Prime meets Optimus at the Gobi Desert in China after an attempt to fight Megatron.
- Megatron's Master Plan Part 1 Megatron has a master plan to flood the entire Earth by melting all of the glaciers on Earth.
- Megatron's Master Plan Part 2 After Optimus and Darkwing fought at Mount McKinely, Starcream attempts to find energon at the Forbidden City. Megatron begins his second part of his evil plan to melt glaciers in Canada.
- Megatron's Master Plan Part 3 Megatron fights Optimus in the sky. Bighorn Prime comes to fight the other Decepticons at the Himalayas.
- Microbots Small spies from space enter Earth to find Megatron. Megatron knew he was being spied on, but not knew who was. he even said that the Autobots aren't doing it.
- Entering Subspace Zone Some humans discovered the Autobots at a fight with Megatron and Darkwing. A human named Freddy hacks into their computer and plants a virus. Ratchet uses his Auto-Ship to stop the virus again. But it was more than a virus. Ratchet has to destroy a type of virus that deletes memory in one second.