Earth

Earth (地球) is the main setting from 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 name, 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.

Earth in the original Mega Man timeline
In the original Mega Man game series, Earth has many similarities with the real life Earth, but including the fictional elements of the series, its technology being more advanced. The whole planet and maps of it can be seen in many games, specially in the stage select screen from Mega Man 8 and Mega Man X5 to Mega Man X8.

Mega Man series
In the 21st century, science advanced greatly, humans being able to create humanoid robots to help in several tasks and that lived peacefully with them. However, in the first Mega Man game, the scientist Dr. Wily plans to take over the world, and Dr. Light modifies the robot Mega/Rock into Mega Man to stop Wily, and starts a series of battles between them.

Mega Man X series
In the 22nd century, technology advanced further and Earth has many futuristic locations. In 21XX, Dr. Cain found Dr. Light's last creation, Mega Man X, inside a capsule, and by analyzing him he is able to creates Reploids. Reploids soon become part of the humans lives, but for unknown reasons, some of them become Mavericks and rebel against humans, leading to the creation of the Maverick Hunters. Not long after, Sigma begins them Maverick Wars, and Earth suffers a large amount of damage during this period, specially in Mega Man X5, were Sigma spreads the Sigma Virus all over the planet and the giant space colony Eurasia crashed.

Elf Wars and 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.

Neo Arcadia

Mega Man ZX series
Legion created laws to give equality between humans and Reploids, and now both are treated equally as humans, living together in harmony.

Game of Destiny

Mega Man Legends series
Several thousand years after the Mega Man ZX series, Earth (known as Terra outside Japan in this series) was covered by water, and humans now live on small landmasses.

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

MegaMan Battle Network series
PETs and NetNavis. World Three.

MegaMan Star Force series
The Earth has changed it's technology from Internet-based to an EM Waves technology, and EM Beings replacing NetNavis. With the use of The 3 Satellites, controlled by the Satellite Admins, the whole Earth is connected using the Sky Wave (and later the Astro Wave), which trenscend to space (Outer Astro Wave) and other planets, such as Planet FM or Planet AM.