Earth

Earth (地球) is the main setting and backdrop for the Mega Man franchise. It is the third planet from the Sun and the densest and fifth-largest of the eight planets in the Solar System. It is also the largest of the Solar System's four terrestrial planets. It is sometimes referred to as the world or by its Latin-language names, Tellus or Terra. Earth is home to millions of species, including humans. Both the mineral resources of the planet, as well as the products of the biosphere, contribute resources that are used to support a global human population. These inhabitants are grouped into about many independent sovereign states, which interact through diplomacy, travel, trade, and military action.

Original Mega Man universe
In the classic Mega Man series Earth has many similarities with the non-fictional Earth, but has much more advanced technology and, if Wily & Right's RockBoard: That's Paradise is taken as canon to any degree, different names for continents and/or nations. The whole planet and maps of it can be seen in many games, especially in the stage select screens from Mega Man 8 and Mega Man X5 to Mega Man X8.

Mega Man series
In the 21st century, with the advancement of science, humans were able to create industrial humanoid robots to help with different tasks, and they coexist peacefully. However, in the first Mega Man game, the scientist Dr. Albert Wily plans to take over the world, and the foremost authority on robotics, Dr. Thomas Light, modifies the helper robot Rock into the super robot Mega Man (Rockman in Japan) to stop Wily, starting a series of battles between the two scientists and their creations.

Mega Man X series
Several years later, Dr. Thomas Light created a robot he named Mega Man X, which is able to think and make its own decisions. He was sealed after then because of the fear of how dangerous he can be to the world. After the discovery of X in the 22nd century, Dr. Cain created Reploids based off X's design. The world eventually turned into two great major factions: Reploids and humans. They lived peacefully for a long while. Unfortunately for Dr. Cain, Dr. Light’s greatest fear came true. The presence of Maverick Virus causes the new robots to rebell against humankind and became powerful enemies known as Mavericks, showing hostile actions against the world's peace. The group was eventually developed larger under control of Sigma, which was stopped ultimately thanks to Maverick Hunters X and Zero.

Several months after the Repliforce war, Earth is at a peaceful time. The repair of the space colonies damaged during the war was almost complete, the only space colony remaining being the giant colony Eurasia located in a Lagrangian point. As it was quite old, it was planned to receive extensive renovation. However, one day someone had occupied Eurasia and took control of it, scattering a virus in the colony and using its artificial gravity systems to set it on a collision course towards Earth. Within 16 hours, Eurasia will crash and cause great destruction, in the worst case extinguishing all life from the planet. The Maverick Hunters plan on using the large particle cannon Enigma to destroy Eurasia before it happens. The Enigma cannon is somewhat old and needs to be upgraded. Signas, the Hunters' new commander, orders Mega Man X and his comrade Zero, as they race against time to collect the four parts necessary to upgrade the Enigma and stop Eurasia before it's too late. To make things worse, Sigma scattered the Sigma Virus all over the world and the parts needed are being protected by Mavericks.

Three weeks Ever since the Eurasia incident in Mega Man X5, the earth has been widely devastated throughout the Mega Man X series. Ruins, deserts and pollution are very common, and humanity spends their lives underground for safety.

after the crash of the Eurasia colony in Mega Man X5, the Earth's surface is badly damaged, and humans have been forced to live underground to survive from the pollution. Reploids have been sent to the surface to attempt to make it livable once again. There was no trace of Mavericks for some days, and the Maverick Hunters help cleaning up the world. Gate, a Reploid scientist who was once a colleague of Alia, stumbles upon the crash site of Eurasia, finding something unusual. After that, Gate became mad and a strange set of Maverick outbreaks occurs, and when X is called to stop a giant Mechaniloid, he sees a purple-like figure that resembles Zero. Around the same time, a powerful Reploid named High Max appears and claims to be investigating the Zero Nightmare, and they fight. High Max, however, proves to be too strong and X cannot damage him with his X-Buster.

A Reploid scientist named Isoc makes an announcement saying that the ghost of Zero, Zero Nightmare, is behind the new Nightmare Phenomena. He sends eight Reploids to investigate areas with high jamming suspected to be infected by the Nightmare to discover the mystery surrounding it and delete Zero's ghost, with High Max leading the mission. Isoc also ask for volunteers to help them. X goes off to the suspected areas to investigate the Nightmare, defeat the Mavericks, and rescue the Reploids that volunteered to help.

During his mission, X fights against the Zero Nightmare and finds the real Zero, who was believed to have been destroyed after the last encounter with Sigma. Signas is reluctant to ask Zero's help as he had just returned, but due to the crisis, Zero helps X in the mission.

After defeating the Mavericks, the Maverick Hunters discover Gate was behind the Nightmare Virus. Gate is impressed with the abilities of X and Zero, and challenges the Hunters to a duel, revealing them the location of his hidden laboratory. In his laboratory, Gate also reveals he was able to create the Nightmare and High Max by analyzing Zero's DNA, which he found in Eurasia's crash site. X and Zero defeat High Max and Gate; Isoc was later found unconscious in a similar way to the Erasure Incident (mentioned by Alia when playing as X). Upon Gate's defeat, Gate reveals he had revived Sigma. Sigma states that he didn't need his help to revive, attacks Gate and retreats. X and Zero rush to stop the partially-reconstructed Sigma and battle him, and although he was not fully complete, he puts up a good fight. In the end, the Hunters prove victorious, defeating Sigma and removing Gate's body from the wreckage of his lab to attempt to repair him.

After the Eurasia and Nightmare incidents that left the Earth's surface devastated, Reploids have worked diligently to clean up the world and make it habitable for humans once again, and is slowly recovering. However, Maverick crime is on a rise. The Maverick Hunters had weakened when X retired from the front lines to assume a support role and achieve more peaceful solutions. To take care of the rising crime, the group of vigilantes Red Alert was created under the command of Red. Initially, they only fought against Mavericks, but one day the group changed and began acting strange. One of their key members, Axl, noticed he was being used and goes AWOL. Red sends a giant Mechaniloid to take him back, but it is stopped with the help of Zero and Axl is taken to the Maverick Hunters headquarters. Red contacts them and issues a challenge - he released some of the Mavericks Red Alert has in custody to various locations around the globe, challenging them to see who can defeat more with Axl as the prize. In the end, it is revealed that Sigma is behind the change of Red Alert, having been drawn to Red Alert after realizing Axl's power. Once again, the Hunters face Sigma and he is defeated. Later, Axl attempts to officially join the Maverick Hunters, even with X's disapproval.

Mega Man Zero series
Shortly after the end of the long lasting Maverick Wars, the Elf Wars occur, a four year long conflict that ended with approximately 90% of all Reploids and 60% of all humans dying. After the war, Maverick Hunters X and Zero have vanished from the view of the public and have become mere legends. Neo Arcadia is created as a paradise for humans, who live peacefully without worries. However, Neo Arcadia is in risk of facing an energy crisis. Unknown to the majority of the population, many Reploids are labelled Mavericks even when innocent to reduce energy comsuption, leading to the creation of a Resistance force in an attempt to save themselves from annihilation.

Ciel, a human scientist, by studying Cyber-elves, hopes to develop a new source of energy that she intends to use to bring peace. Until then, their fight continue. Ciel revives the ancient warrior Zero, who had been locked away for an unknown span of time. Zero finds himself facing the past when he battles Copy X, a duplicate of his historic partner, and leader of Neo Arcadia, the primary human government. The original X appears, in the form of a Cyber-elf. His body was sacrificed in an attempt to imprison the Dark Elf, the source of the Elf Wars. Now X serves primarily as a source of guidance. Meanwhile, Dr. Weil, a scientist banished from Neo Arcadia for instigating the Elf Wars using a Reploid known as Omega, returns with a vengeance to attempt to accomplish his goals once and for all. He takes over Neo Arcadia and makes prisoners out of the humans as much as he wages war against the Reploids. He and his plan was ultimately defeated with the heroic sacrifice of Zero.

Mega Man ZX series
After the fighting against Neo Arcadia came to an end, Ciel and her research team comes across the remains of Doctor Weil's core, also named it Model W. Model W began to turn members of Ciel's team into Mavericks. Dr. Ciel's fate is unknown, so Alouette, a young Reploid raised by Ciel, assumes command of the Guardians. A new law is created by the Legion, were Reploids must have lifespans and humans have mechanical parts integrated into their bodies, and now both are treated equally as humans, living together in harmony. One member of the Sage Trinity, Master Albert, created the Game of Destiny and made Mega Men fight against each other by using Biometal, and finally against Albert and Model W.

Mega Man Legends series
Several thousand years later, Earth (known as Terra outside Japan in the Mega Man Legends series) was covered by water, and humans now live on small landmasses. The original humans live on Elysium while bionic humans known as Carbons live on Terra. Before dying, The Master asked Mega Man Trigger to protect the Carbons and destroy the System, resulting in a series of battles that ended with Mega Man and Sera being sealed by Yuna for several years, and those events became legends. One day, the Digger Barrell Caskett found Mega Man Trigger sealed in a ruin and adopted him, naming him Mega Man Volnutt.

Of note, the map in Mega Man Legends 2 has 32 lines. As the Mega Man Legends series has the same unit of time as the classic series, those lines may not be for time zones like the Coordinated Universal Time, but a chart like the rhumbline network.

Mega Man Battle Network universe
Unlike the original series, the locations of the Earth from the Mega Man Battle Network and Mega Man Star Force series use fictional names, but still share many similarities to the real life Earth.

Mega Man Battle Network series
In 200X, most people have a PET (PErsonal Terminal) with a NetNavi. Humans use the humanoid NetNavis housed in their PETs for general use as Operators, although some work with their Navis in a sport called NetBattling, where an Operator uses Battle Chips to give their Navis special abilities to fight with, such as giving a sword or bomb. The series is centered around young Lan Hikari and his Navi, MegaMan.EXE, who both love to Net battle, and their adventures in the world, such as participating in a tournament (third and fourth games), or stopping the Net-criminal organizations like World Three, Gospel and Nebula.

Mega Man Star Force series
200 years later, the Internet-based technology was replaced to an EM Wave-based technology, which created the Wave Road exists in the real world, EM Beings replace NetNavis, and no one uses a PET anymore. They're all invisible to the human's vision. With the use of three satellites, controlled by the Satellite Admins, the whole Earth is connected using the Sky Wave (and later the Astro Wave), which transcend to space (Outer Astro Wave) and other planets, such as Planet FM and Planet AM. The series centers around Geo Stelar, a young boy who lost his dad Kelvin Stelar in a space accident, and the fugitive AM-ian, Omega-Xis, who can change Geo's frequency in a way called EM Wave Change, who lost his father, fighting villains such as other FM-ians and other antagonists, such as Le Mu and Dealers and finally found him in Meteor G core.

Trivia

 * If Eurasia crashes on Earth Mega Man X5, the picture of Earth in the stage select screen will drastically change, showing how much damage it suffered. However, Earth has its original appearance in Mega Man X6 onward, showing that canonically the impact's damage was reduced by the efforts of the Maverick Hunters.
 * In Mega Man Legends, there is an old world map on Barrell Caskett's room that is different from the Earth shown in the classic and X series, but Mega Man Volnutt says it is different from the planet's current appearance.