In the Cenozoic era, six interplanetary warriors, the Power Rangers, are tasked with protecting life on Earth and the Zeo Crystal. The Green Ranger, Rita Repulsa, betrays them and plans to dominate the universe. The Red Ranger, Zordon, survives Rita's attack and hides five of the Rangers' power source, the Power Coins. He orders Alpha 5, his robotic assistant, to perform a meteor strike that kills him, the dinosaurs, and sends Rita to the bottom of the sea, foiling her scheme.
In 21st-century Angel Grove, high school football star Jason Scott is dismissed from the team and placed under house arrest after a failed prank. In detention, he encounters Billy Cranston and Kimberly Hart. After defending Billy from a bully, Billy offers to deactivate Jason's ankle monitor for help at an old gold mine that evening. Once there, Jason leaves to explore and runs into Kimberly. Billy detonates explosives to break some rock, attracting the attention of Jason, Kimberly and nearby students Trini and Zack. The five discover the Power Coins and each take one. While escaping mine security, their car is hit by a train. The five find themselves at home the next morning and discover that the coins have granted them superhuman abilities. Elsewhere, Rita's body is found. Waking, she goes on a rampage, hunting pieces of gold to raise her minion Goldar to find the Zeo Crystal.
The five teenagers return to the mine and discover an ancient spaceship where they meet Alpha 5 and Zordon's consciousness. They inform the teenagers about the Rangers history and Rita, warning that they have eleven days until Rita has her full power, finds the Zeo Crystal, and uses it to destroy life on Earth. The five leave the ship with no intention of returning until Zordon pleads with Jason to convince the team.
The five return to train the next day, but they cannot morph. They spend the next week training against simulated Putties and trying unsuccessfully to morph. To inspire the Rangers, Alpha reveals the Zords. Zack takes his Zord out for a joyride and almost kills the other Rangers when he crashes it. This angers Jason, and they fight. While trying to separate the two, Billy spontaneously morphs. However, when he becomes conscious of it, the armor disappears. Angered at their lack of progress, Zordon dismisses the group. Jason returns to the ship to confront Zordon and discovers that once the Rangers morph, it will open the Morphing Grid and allow Zordon to restore himself in a physical body. Feeling betrayed, Jason accuses Zordon of using the team for his own benefit. That night, the team camp at the mine and bond with each other.
Later that night, Rita attacks Trini and orders her to bring the Rangers to the docks. Trini informs them about Rita and they arrive to fight, but are quickly defeated. Rita forces Billy to reveal the location of the Zeo Crystal, which he'd figured out, kills him, and releases the others. The Rangers take Billy's body to the ship and ask Zordon to resurrect him. The Rangers agree they would give their lives for each other and resolve to defeat Rita. In doing so, they unlock the Morphing Grid. Zordon revives Billy, sacrificing being able to restore his physical self. With the team restored and confident, the Rangers morph into their armor.
Rita creates Goldar, raises an army of Putties, and attacks Angel Grove to find the Zeo Crystal. The Rangers battle the Putties and head to Angel Grove in their Zords. After the Rangers destroy the Putties, Goldar pushes the Rangers and their Zords into a fiery pit. In the pit, the Zords combine and form the Megazord. Rita merges with Goldar. The Rangers battle and destroy Goldar. After refusing Jason's offer to surrender, a defiant Rita tells the Rangers that more will come for the crystal and leaps at the Megazord only to be slapped into space. The Rangers are praised as local heroes, and with Rita's threats foiled, they return to their normal lives while keeping their powers.