Elec Man is a Robot Master from the classic Mega Man series. He was built by Dr. Light to control electrical operations. Elec Man manages nuclear power plants and is capable of generating electricity. He can expel over 500,000 volts from his fingertips. Elec Man is very fast and his powerful Thunder Beam can destroy Mega Man in three hits. This was changed in later titles, but his speed and attacking power, along with new lightning-based attacks, still make him a force to be reckoned with, and is still one of the most feared opponents in the original game.

Ice Man is one of the first six (eight in Mega Man Powered Up) Robot Masters from the original Mega Man series. He was built by Dr. Light to perform human-like tasks under extreme climate conditions. This can be done due to the fact he is impervious to chilling sub-zero temperatures. Contrary to popular belief, he is capable of functioning in hot environments, though he is less powerful there.

Fire Man is a Robot Master from the original Mega Man series. He was built by Dr. Light to work in an incinerator at a waste management facility and is able to wield flames that can reach 7000-8000 degrees.

Cut Man is one of the first six (eight in Mega Man Powered Up) Robot Masters from the original Mega Man series, created by Dr. Light to be a timber-felling robot. Cut Man first appeared in the first Mega Man game, where he was reprogrammed by Dr. Wily to help him conquer the world. Cut Man is found to be somewhat formal as he addresses other robots as "Mr." or "Ms." (either this or it shows that his A.I. age is younger). His Rolling Cutters are made of highly resistant "ceramic titanium", and are extremely sharp, being easily able to cut through metal.

Quick Man is a combat Robot Master created by Dr. Wily using Elec Man's design as a base. Quick Man is made of lightweight materials, allowing him to move at very high speeds. Though his top running speed is unknown, Quick Man is one of the fastest Robot Masters in the Mega Man series possessing a standard cruising speed of Mach 5. His weapon is the Quick Boomerang, small boomerang cutters that he can shoot from his right arm. Because of a defect, Quick Man is vulnerable to Flash Man's Time Stopper. Quick Man and Turbo Man are also rivals. His level in Mega Man 2 contains a number of deadly lasers known as Force Beams.

Bubble Man is the first aquatic Robot Master created by Dr. Wily for underwater combat. However, a defect in his system makes him unable to walk underwater, being only able to move by jumping. After seeing this, Wily couldn't help but laugh at his way of moving. Despite this flaw, Bubble Man is able to swim. This problem has been fixed in Mega Man 2: The Power Fighters.

Bubble Man attacks with normal shots from his arm cannon, and can shoot Bubble Lead shots from his arm cannon and the gun on the top of his head. Bubble Lead are durable bubbles mixed with sulfuric acid that can be used for several purposes, like hitting opponents with small bubbles, wrapping opponents inside large bubbles, or protecting Bubble Man himself.

Flash Man is a Robot Master created by Doctor Albert Wily. In combat, Flash Man can stop time to attack opponents while they cannot move with the rapid-firing blaster in his right arm. To his enemies, it appears Flash Man is moving at light speed or teleporting. It is believed that this ability is a perfected form of what the Robot Master, Time Man, was capable of. However, unlike Time Man, who could only slow down time with Time Slow, Flash Man can stop it completely with Time Stopper.

Heat Man is a combat Robot Master created by Dr. Wily based on Fire Man's design. His body is highly resistant to heat and fire, and has the shape of a Zippo lighter, the lid sometimes shutting down unintentionally, usually when he guffaws. He has a dial in his back that regulates the power of his flames, which he's unaware of. His main weapon is Atomic Fire, which can produce flames up to 21,632 degrees Fahrenheit (12,000 degrees Celsius). He can surround himself in flames for protection, making him invulnerable for a short time, and tries to tackle enemies while on fire. He can also spit fire from his mouth and project enormous fire blasts from his hands.

Enker was the first robot from the "Mega Man Killer" series built by Dr. Wily, the only purpose of which is to destroy Mega Man. In Mega Man: Dr. Wily's Revenge, he appears after the second set of Robot Masters is defeated. His Mirror Buster allows him to absorb shots into his spear (called the Barrier Spear) and fire them back at Mega Man as either small buster shots or large waves, depending on the amount of shots taken.