- Mega Man
- Dr. Wily
- Dr. Light
- Concrete Man - A robot whose purpose was dam construction. He has incredible pride in his own craftsmanship, and if he discovers other worker robots cutting corners, he will angrily tell them off. Concrete Man's weapon, Concrete Shot, creates a temporary foothold as soon as it touches the ground. It can also be used to stop enemies in their tracks.
- Galaxy Man - An assistant robot at a space laboratory. He has a brain that can instantly perform calculations of rocket trajectories. His weapon is the Black Hole Bomb. It creates a black hole that sucks up projectiles and enemies.
- Hornet Man - A robot who manages a flower theme park. He possesses knowledge pertaining to flowers from around the world. His special weapon is the Hornet Chaser. It fires a bee-like device the pursues its targets.
- Jewel Man - A robot that works in a diamond mine. He is in charge of polishing work with his skilled fingers. His special weapon is the Jewel Satellite. It protects the body with rotating diamonds.
- Magma Man - A robot created for safety management at a geothermal power plant. He is able to work efficiently even amidst magma thousands of degrees in temperature. His hobby is touring hot springs, and not only does he enjoy soaking in them, he explains the components and benefits of the hot spring waters to other guests. His primary weapon is the Magma Bazooka, which allows him to launch powerful fireballs in multiple directions.
- Plug Man - A line inspection robot at a television set factory. He carries out the final check on the products with a sharp eye. His special weapon is the Plug Ball. It fires a plasma ball that runs along the ground.
- Splash Woman - A robot who performs rescue work in situations such as sinking ships and people in oceans. Her special weapon is the Laser Trident. It fires a laser that has penetration ability.
- Tornado Man - A robot who was permanently stationed at a weather regulation site created in mid-air, before suddenly participating in the robot revolt. He was built with equipment that allows him to create powerful tornadoes, and the general nature of his work was to offset developing tropical storms with his tornadoes. Tornado Man's weapon, the Tornado Blow, launches a huge tornado that covers the entire game area. Heavy enemies will take damage, but lighter ones will be blown entirely off-screen.
- Fake Man - (downloadable) - a robot created by Dr. Wily to impersonate a police officer and arrest Dr. Light during the revolt of the Light Numbers.
To be added...
Mega Man's creator Dr. Light is blamed for a robotic rampage, and Dr. Wily himself has no apparent connection to it (even showing a video of Dr. Light declaring world domination and Dr. Wily refusing to follow him), announcing that he needs donations to complete the robots he created to combat those of Dr. Light. Mega Man must fight to prove his creator's innocence and expose Wily's true intentions.
- Mega Man 9 is the first game in the series to feature a female Robot Master: Splash Woman.
- Although Bass does not appear directly in the game, he does make a cameo appearance. In the background at the end of the game, players can see his image on Wily's computer.