Godzilla Against Mechagodzilla (ゴジラ×メカゴジラ, Gojira tai Mekagojira) is a 2002 Japanese kaiju film directed by Masaaki Tezuka, with special effects by Yūichi Kikuchi. Distributed by Toho and produced under their subsidiary Toho Pictures, it is the 27th film in the Godzilla franchise and the fourth film in the franchise's Millennium period, and is also Toho's 26th Godzilla film. The film features Godzilla, along with an updated version of the mecha character Mechagodzilla, who is referred to in the film by its codename MFS-3 Kiryu. The film stars Yumiko Shaku, Shin Takuma, Kou Takasugi, Yuusuke Tomoi, Kumi Mizuno, and Akira Nakao, with Tsutomu Kitagawa as Godzilla and Hirofumi Ishigaki as Kiryu.

Rather than continuing the format of the other films in the Millennium era of ignoring the events of every installment in the Godzilla film series aside from the original 1954 Godzilla. Godzilla Against Mechagodzilla takes place within a continuity that alludes to some of Toho’s Showa-era kaiju films. A direct sequel, Godzilla: Tokyo S.O.S., was released on December 13, 2003.

Forty-five years after the first Godzilla's attack and death, maser-cannon technician lieutenant Akane Yashiro of Anti-Megalosaurus Force (AMF) is unable to kill a new member of Godzilla's species during her first fight with him at Tateyama. During the battle, she panics and accidentally knocks a jeep off the road, where Godzilla steps on it, killing her comrades inside.

As a result, Akane is demoted while scientists, including single father Tokumitsu Yuhara, are gathered to build a cyborg mecha from the first Godzilla's skeleton. In time, the "MFS-3 Kiryu" is finished and inducted into the Japan Xenomorph Self-Defense Forces (JXSDF) along with its human pilots, the Kiryu Squadron, with Akane as the primary pilot. However, memories of her actions during the first battle still linger as one of her squadron mates, 2nd lieutenant Susumu Hayama, hates her because his brother was among those killed.

Four years later, Kiryu is unveiled in a global presentation where its remote systems, use of command aircraft, and Absolute Zero Cannon are shown. Simultaneously, Godzilla returns and Kiryu is launched into battle. In the midst of this, however, Godzilla's roar causes Kiryu to experience memories of its past life and go berserk while Godzilla retreats. The horrified Kiryu Squadron is powerless to stop the rampaging Kiryu until it runs out of energy and is brought back to headquarters for repairs.

Meanwhile, Akane deals with Hayama's attempts to make her leave and Yuhara's attempts to get to know her despite her desiring solitude, though she begins to develop a bond with Yuhara's young daughter Sara. As Godzilla mounts another attack, the repaired Kiryu is deployed and confronts Godzilla once more. Kiryu gains the upper hand, but as it prepares the Absolute Zero Cannon, Godzilla knocks Kiryu away with his atomic breath and diverts the blast. With Kiryu disabled and the remote piloting system offline, Akane orders Hayama to land his command craft so that she can use Kiryu's internal backup cockpit. Before she leaves, Hayama wishes her luck, forgiving her.

Piloting Kiryu directly, Akane closes in on Godzilla, hoping to use the Absolute Zero Cannon at point-blank range. As the two monsters collide, Akane uses Kiryu's thrusters to propel them out to the ocean before firing. In the aftermath, an injured Godzilla retreats while Kiryu is heavily damaged. With Kiryu successful in repelling Godzilla, it is taken back to base for repairs.

In a post-credits scene, Akane agrees to have dinner with the Yuharas and salutes Kiryu.