Mega Man Zero is a series in Capcom's Mega Man video game franchise. It was developed by Inti Creates, with Co-Producer Keiji Inafune and Director Yoshinori Kawano. The series consists of four games that were first released on the Game Boy Advance and later on the Nintendo DS and the Virtual Console (Wii U).

The story plays 100 years after the Mega Man X storyline and follows the re-awakened Zero, who is fighting in a war between humans and Reploids, self-aware, human-like robots who are oppressed and hunted down by mankind due to a worldwide energy shortage crisis. Together with the human scientist Ciel, Zero helps the Reploid resistance survive and fights against other Reploids sent by mankind to destroy them. However, this is only the setup for the story and events change drastically throughout the series.

Similar to the Mega Man X series, the Mega Man Zero series is a two-dimensional action platform game with run and gun elements that places a heavy emphasis on memorizing boss patterns and selecting the correct weapons to use against enemies.

Unlike the previous series, the stages of Mega Man Zero are inside of areas that are part of a larger map, and the player can freely explore these areas once the respective mission(s) in each area is completed. However, Mega Man Zero 2 and later entries removed this and returned to the traditional Mega Man format that allowed the player to select a mission from a stage select screen.

The game mechanics slightly change with every entry of the series. Zero is given a variety of weapons to use and can level them up to unlock new abilities, although this was removed from Mega Man Zero 3 and onward as the abilities become accessible from the start of the game.

A new entry in the series was the Score and Level System, which gives the player a score out of 100 and its corresponding level[b] depending on how well they performed on each mission. The series also introduces the Cyber-Elf system, which allows Zero to equip small helper beings known as "Cyber Elves" to assist him in combat. After feeding them with a certain amount of E-Crystals that are dropped by enemies, the elves can either provide permanent enhancements—such as increasing Zero's maximum health capacity, or grant temporary benefits—such as the ability to deflect bullets for a short time. However, the score at the end of each mission will decrease for every Cyber-Elf used.

Finally, Zero's weapons receive elemental enhancements in every game except Mega Man Zero 4. Acting like a rock-paper-scissors system, Zero gains three element chips (Fire, Ice, Thunder) that can be attached to all his weapons and changed freely. Doing so adds elemental effects to his charge attacks and inflict higher damage to bosses weak to the selected element, or no damage if they are immune to it.