Metroid: Samus Returns is a 2017 action-adventure game developed by MercurySteam and Nintendo EPD and published by Nintendo for the Nintendo 3DS handheld game console. It is a remake of the 1991 Game Boy game Metroid II: Return of Samus. Players control series protagonist Samus Aran, a bounty hunter who is contracted by the Galactic Federation to exterminate the parasitic Metroid species on their home planet of SR388. While the story and structure parallel the original game, Samus Returns features redone graphics, updated controls and user interface, and new gameplay mechanics not seen in previous 2D Metroid titles, such as a melee counterattack and the ability to aim freely at any angle.

Development began in 2015, overseen by longtime producer Yoshio Sakamoto and directed by Takehiko Hosokawa, a game designer in the series. MercurySteam originally pitched a remake of Metroid Fusion before Sakamoto suggested remaking Metroid II. New gameplay features and areas were added to "spice up" the experience of the original game. Music was composed by Daisuke Matsuoka and directed by Kenji Yamamoto, who had co-composed the music for Super Metroid.

Samus Returns received positive reviews upon release for its visuals and improvements over the original version, with many also deeming it a return to form for the series. Some criticism was given to the controls and the counterattack mechanics. It received awards and accolades from multiple publications and awards shows, including "Best Handheld Game" at The Game Awards 2017, and "Handheld Game of the Year" at the 21st Annual D.I.C.E. Awards. Sakamoto was impressed with MercurySteam's understanding of the series, leading to their continued collaboration for Metroid Dread (2021) on the Nintendo Switch.

Metroid: Samus Returns is a side-scrolling game presented in a 2.5D perspective. Players control series protagonist Samus Aran, a bounty hunter who explores labyrinthine environments, defeats hostile aliens, and collects power-ups to access new areas. Samus Returns is a remake of the 1991 Game Boy game Metroid II: Return of Samus; it features a story and structure similar to the original game but includes updated controls, visuals, and gameplay.

The game introduces several features new to the side-scrolling Metroid games. Samus can perform a Melee Counter with her Arm Cannon to stun nearby enemies that use physical attacks. A visual cue indicates when an attack can be countered. Successfully countering an enemy places Samus in an advantageous position; against Metroids, her next shot will be fully charged, and she can fire several Missiles at them. In Metroid II, her firing direction was limited to specific angles, but in Samus Returns, she can fire freely in any direction. Samus also gains access to new abilities called Aeion abilities, which use an energy gauge. One example of an Aeion ability is the Scan Pulse, which allows Samus to scan the surrounding environment for hidden pathways and items. The game also includes Teleport Stations, enabling Samus to fast travel between areas. Several abilities introduced after Metroid II return in Samus Returns, such as the Grapple Beam, Power Bombs, and Super Missiles.

Samus Returns supports Amiibo figurines, with compatible figures based on the Metroid series. Scanning these figurines can unlock reserve tanks and a Metroid Marker, which helps locate nearby Metroids. After completing the game at least once, players can unlock Amiibo-exclusive content, including a Metroid II art gallery, a Samus Returns art gallery, a Sound Test, and Fusion Mode, an extra-hard difficulty setting featuring Samus's Fusion Suit. A standard Hard Mode is also unlocked upon completing the game, which does not require an Amiibo.

In the year 20X5, a lone bounty hunter named Samus Aran is sent by the Galactic Federation to infiltrate the Space Pirate base on the planet Zebes, where she foils the Pirates' plans to use the parasitic organisms called Metroids and defeats the Pirate leader, the Mother Brain. Seeing the threat posed by the Metroids, the Federation sends a special squadron of elite soldiers to the Metroids' home planet of SR388 to investigate, but the squadron soon goes missing. After retrieving a small sampling of data confirming a Metroid presence within the planet, the Federation sends Samus to SR388 to destroy the species.

Samus lands on the surface of SR388 and explores the planet, traveling through its caverns. She encounters the Metroids in different metamorphosis stages, growing from small jellyfish-like creatures to large reptilian beasts. After killing most of the planet's Metroids, Samus finds and destroys the Queen Metroid. Shortly afterward, Samus discovers a Metroid egg that hatches in front of her. The Metroid hatchling imprints onto Samus, thinking she is its mother. Refusing to kill the infant Metroid, Samus decides to take it with her. As Samus and the infant Metroid reach the planet's surface to return to her gunship, they are attacked by a half-mechanical Ridley. After a long battle, Ridley is defeated, and Samus, along with the Metroid, leave the planet together. In a post-credits scene, a Hornoad wanders on the planet's surface, gnaws on Ridley's discarded mechanical claw before suddenly being killed and copied into a vicious form by an X Parasite.