Mega Man IV, known as Rockman World 4 (ロックマンワールド4, Rokkuman Wārudo Fō) in Japan, is a video game developed by Capcom for the Nintendo Game Boy. It is the fourth installment in the handheld version of the Mega Man series. The game continues the quest of the protagonist Mega Man in a never-ending struggle with his long-time arch nemesis Dr. Wily, who sends out a disruptive radio signal to cause a rampage, city-wide destruction from dorment robots. Mega Man IV features the traditional action platforming gameplay of the prior games while introducing one new feature, the ability to purchase items with power-ups found throughout each stage. As with previous Game Boy releases, the game incorporates gameplay elements and bosses from two sequential Nintendo Entertainment System (NES) games: Mega Man 4 and Mega Man 5. The game has received a warm critical reception.

At its core, the gameplay is still the same as the previous 3 Mega Man Game Boy games. The player takes on the role of Mega Man as he traverses a series of two sets of selectable action/platforming stages in any order desired. The player's initial weapon, the "Mega Buster", can fire both small shots and much larger and more powerful, charged blasts. Each stage is populated with various types of enemy robots and a single Robot Master exclusive boss. Beating the Robot Master will earn the player its special "Master Weapon" for use throughout the rest of the game. Clearing 2 of the Robot stages also gives the player access to abilities from Mega Man's dog Rush, who can transform into a springboard for reaching high platforms or a jet for crossing large distances. Also, the game's first four Robot stages each house a letter ("B-E-A-T") that spell out the name of the bird Beat. Collecting all 4 letters endows the player the ability to summon upon Beat to assist by attacking enemies. On the other hand, the game's latter four Robot stages each house letters that spell ("W-I-L-Y") which would be imperative to collect in entering to the first part of Dr. Wily's fortress. The stages also contain hidden passages where the character Proto Man leaves the player items, often giving "Super Tanks" that refill all weapons energy and health energy.

Mega Man IV carries on the Game Boy line's tradition of recycling elements from two consecutive Mega Man NES releases, most prominently with its bosses. The first four Robot Masters (Toad Man, Bright Man, Pharaoh Man, and Ring Man) are originally from Mega Man 4 and the latter four (Crystal Man, Napalm Man, Stone Man, and Charge Man) are from Mega Man 5.Mega Man IV also introduces a shop feature to the series. In addition to various restorative items like health, weapon power, extra lives, energy tanks that can be stored for later use, the player can pick up "Power Chips (P-Chips)" dropped by enemies or in designated spots in the stages. Dr. Light's lab can also be visited from the stage select screen, wherein the player can purchase various items using the P-Chips collected. One such item is the newly introduced "Auto Charger" (or "Energy Balancer"), which automatically takes weapon energy capsules and restores it in the weapon with the least amount of energy left, provided that there is no refillable special weapon selected.