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 Mega Man classic series Earth has many similarities with the non-fictional Earth, but has much more advanced technology and, if Wily and 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, science advanced greatly, and humans lived peacefully with the humanoid robots they'd built to help with different tasks. However, in the first Mega Man game, the scientist Dr. Albert Wily plans to take over the world, and Dr. Thomas Light modifies the robot Mega/Rock into Mega Man/Rockman to stop Wily, starting a series of battles between the two scientists.

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 instigates the Maverick Wars, and Earth suffers a large amount of damage during this period, especially in Mega Man X5, where 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 Wave technology, and EM Beings replace NetNavis. 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.