Pacific Rim

 In the near future, giant monsters identified as Kaijus have risen from a portal in a crevasse beneath the Pacific Ocean, resulting in a war that takes millions of lives and quickly consumes humanity's resources. To combat the monsters, a special type of weapon is designed: massive, humanoid fighting machines, known as Jaegers, which are controlled simultaneously by two pilots whose minds are bound in a neural link which lets them share the mental strain which would otherwise overwhelm a single pilot.

The Jaeger program is initially successful in fending off Kaiju attacks and at first turns the tide of the war. However, over time, Kaijus cross through the portal at a faster rate, with each new Kaiju becoming increasingly well-adapted for fighting the Jaegers. As such, the robots become less effective, causing the now-united governments of Earth to lose faith in the Jaegers' ability to defend humanity. The Jaeger program is terminated, with resources diverted to building the "Wall of Life", a coastal fortification to protect Earth's cities. The four remaining Jaegers are redeployed to Hong Kong to defend the unfortified coastline until the wall can be completed. Stacker Pentecost, commander of the Jaeger forces, devises a plan to end the war with an illegally-acquired Russian nuclear warhead.

Pentecost approaches former pilot Raleigh Becket and convinces him to return to the program. Becket and his brother Yancy had once been pilots of Gipsy Danger and tasked with defending the Alaskan coastline. During a mission, they ignored an order and engaged a Kaiju directly. Yancy was killed while connected to his brother, traumatizing Raleigh. Upon returning to the program, Raleigh undergoes a rigorous process of testing to find a new co-pilot, since the stronger the connection between two pilots, the better their performance in battle. Raleigh demands to be partnered with Mako Mori, a test pilot whose participation Pentecost opposes, as Mako is his adoptive daughter. He eventually relents and allows her to partner Raleigh. The duo's initial test run nearly ends in disaster when Mako gets caught up in a childhood memory of a Kaiju attack; she inadvertently activates and nearly discharges Gipsy Danger's weapons system while in the hangar. The duo are withdrawn from the field indefinitely as the remaining Jaegers are tasked with fending off a double Kaiju attack. The defense of Hong Kong goes poorly, with the Kaijus quickly destroying two Jaegers and disabling a third. Pentecost has no choice but to authorize Raleigh and Mako to mount a last stand, and the duo drive off the assault.

Meanwhile, Dr. Newton Geizler—a scientist studying the Kaijus—assembles a machine allowing him to establish a mental link with a Kaiju brain fragment in the way Jaeger pilots connect with one another. The experience nearly kills him, but he discovers the Kaijus are actually artificial weapons sent to Earth as an invading force to allow their masters to colonize the planet. With Pentecost's approval, he seeks out Hannibal Chau, a major figure in the trade of illegal Kaiju parts, in an attempt to get a new Kaiju brain to repeat the experiment. Chau criticizes Geizler's foolishness in merging with the Kaiju brain, as he has now attracted their attention, and the Kaiju attacking Hong Kong are specifically seeking him. After Gipsy Danger kills the Kaijus attacking the city, Chau and his crew of poachers move in to harvest parts. Geizler realizes, too late, that the Kaiju is pregnant. Chau and his crew are attacked by the newborn Kaiju, which is unable to survive outside the womb and dies after eating Chau. Geizler and his skeptical colleague Hermann Gottlieb merge with the baby Kaiju's intact brain, where they discover the secret controlling the flow of Kaijus through the portal.

The Jaeger forces reassemble, planning to use the nuclear warhead to destroy the portal. Pentecost, revealed to have been one of the original Jaeger pilots, takes command of Striker Eureka as one of its usual pilots was injured during the defense of Hong Kong. Pentecost ventures out into the ocean depths, with Raleigh and Mako supporting him aboard Gipsy Danger. Geizler and Gottleib inform them that the portal has a fail-safe system to control the passage of Kaijus, and will only allow them entry if they can mimic a Kaiju's genetic code. Before they can process this information, they are attacked by a trio of Kaijus, including the largest Kaiju in recorded history. Pentecost detonates the warhead, destroying his Jaeger and its pilots, in order to kill the remaining Kaijus guarding the portal. Raleigh and Mako seize a Kaiju's corpse and use it to pass through the portal, intending to overload Gipsy Danger's nuclear reactor to use it as an improvised bomb. With the Jaeger critically damaged by the fight, Raleigh ejects Mako and manually overrides Gipsy Danger's safety protocols before ejecting himself. Gipsy Danger detonates on the other side of the portal, destroying it and the alien commanders, as the two pilots emerge safely on the sea's surface.