Mega Man & Bass is an action-platform video game developed and published by Capcom. It is a spin-off game in the original Mega Man series and was originally released in Japan for the Super Famicom on April 24, 1998. It was later ported to the Game Boy Advance (GBA) handheld in 2002, and localized in English and released the following year.

After defeating the evil Dr. Wily many times, the robotic hero Mega Man is called into action once again when a powerful being known as King steals the blueprints to the creations of Dr. Wily and Dr. Light in order to create an army for robotic dominance over humans. Having learned of the threat, Mega Man's rival Bass decides to take matters into his own hands. The game is an action-platformer where the player advances by defeating bosses and acquiring their signature weapons. Mega Man & Bass lets the player choose between either of its title characters, each of which plays differently from the other.

Mega Man & Bass debuted on the aging 16-bit Super Famicom despite the series having already transitioned to the PlayStation and Sega Saturn with Mega Man 8. Producer Keiji Inafune claimed Mega Man & Bass was created with regard to younger players who did not yet own one of the more advanced gaming systems. The game received positive remarks from critics for its graphics and use of a tried-and-true gameplay formula, though many found the difficulty to be too steep. Although Mega Man & Bass shares many traits with previous console games in the series, Mega Man 9 would not be released until 2008.

The gameplay in Mega Man & Bass is similar to earlier games in the series. The player is tasked with completing a series of action-platform stages while overcoming obstacles, solving minor puzzles, and battling enemies. Destroying the "Robot Master" boss at the end of a stage lets the player acquire its special weapon. In previous games, the player generally took on the role of the hero Mega Man. In this game, the player can choose to start the game as either Mega Man or Bass. However, whichever character is picked must be used for the rest of the game and cannot be changed. Mega Man is able to charge his shots to make them more powerful and has the ability to slide along the ground. Bass is able to rapidly fire his arm cannon in eight directions, though shots cannot be fired while moving or pass through walls unless a certain upgrade is obtained. Bass is also able to double-jump (jump a second time in mid-air) and dash along the ground. Performing both simultaneously lets him cross great distances by doing a dash-jump.

The stage structure is different from other games in the series. After the introduction level, the player can only choose between three Robot Masters. Defeating Cold Man unlocks Burner Man and Pirate Man; defeating Astro Man unlocks Dynamo Man, Tengu Man, and Pirate Man; and defeating Ground Man unlocks Magic Man and Tengu Man. Clearing one of these unlocked stages opens the way to a security room where the player must destroy a series of crystals with obtained Robot Master weapons. Bypassing all eight crystals opens the way to the fortress stages. In a similar fashion to previous installments in the series, enemies often drop bolts after they are destroyed, and these can be exchanged for various restorative items and upgrades. However, unlike in Mega Man 7 the security cavern offers a way to obtain large amounts of bolts without having to repeatedly visit stages. Some upgrades are unique to either character, such as Mega Man's ability to call on his dog Rush to search for items, or an adaptor for Bass to combine with his wolf Treble to temporarily fly. Also distributed throughout the introduction and Robot Master levels are a collection of 100 data CDs that contain information on many prominent characters in the series. Most of the CDs are hidden either behind obstacles that need to be destroyed with a special weapon or accessed with a character-specific ability, making it impossible to collect them all on a single playthrough. CDs collected in each playthrough are permanently placed in a database and remain unlocked after beating the game. Saved games are used in place of the series' traditional password system.