Bases Loaded, known in Japan as Moero!! Pro Yakyuu (燃えろ!!プロ野球, lit. "Burn!! Pro Baseball"), is a baseball video game by Jaleco that was released in Japan. A version for the Nintendo Entertainment System was released in 1987 in Japan and in 1988 in North America, and a Game Boy port was released in 1990. A mobile phone version exists as well. Bases Loaded was released on April 7, 2008 in Japan and on April 12, 2008 in North America for Wii's Virtual Console, at the cost of 500 Wii Points.

The game is the first installment of the Bases Loaded series, followed by seven sequels across three generations of consoles. There are three more video games in the Bases Loaded NES series, Bases Loaded II: Second Season, Bases Loaded 3 and Bases Loaded 4. There was also a Game Boy version of Bases Loaded. The series continued onto the SNES platform with Super Bases Loaded, Super Bases Loaded 2, and Super Bases Loaded 3. The final entry to the series was Bases Loaded '96: Double Header, released for the Sega Saturn and PlayStation.

Bases Loaded is also the first in a series of eight sports Famicom games known in Japan as "Moero!!". This series is all generic sports games. Three of the games were localized in the Western Markets as Bases Loaded, Bases Loaded II: Second Season and Bases Loaded 3, while the basketball game was localized as Hoops. Four titles went unreleased in North America or in the PAL regions.

The game allows the player to control one of 12 teams in either a single game or a full season. For single games, there is also a two-player option.

Bases Loaded featured a unique television-style depiction of the pitcher-batter matchup, as well as strong play control and a relatively high degree of realism, which made it one of the most popular baseball games of the early NES.

One unique feature of the game is that the pitcher can provoke a batter to charge the mound. Each team has only one batter (usually the team's best hitter) who can be provoked in this manner, however; it is up to the player to discover who it is.

At the time Bases Loaded was released, few video games were licensed by North American major league sports. Therefore, the league depicted in Bases Loaded is a fictitious league of twelve teams. They are:

• Boston - has above-average starting pitching with Bopper, Fine, and Page; a strong bullpen; and a powerful lineup powered by Freida, Norkus, and Angel
• D.C. - carries a great offense led by Doreo, Fendy, and Boro but has below-average starting pitching and an average bullpen
• Hawaii- has a strong hitting lineup led by Brutus, Debro, and Moon; reasonable starting pitching; and an average bullpen
• Jersey - boasts the most explosive offense in the game anchored by Paste (best hitter in the game with a .467 avg. and 60 HRs), Bay, and Ford but has starting and relief pitching that is average at best, unreliable at worst.
• Kansas - features a starting rotation led by Patson, who has the fastest fastball in the game (102 mph) and good relief pitching, but an average offense, led by Patty and Baker, that has decent power but low hitting averages
• L.A. - features a lineup with decent hitting averages but little power led by Wales and Bacon but has an average starting rotation led by Tucker and mediocre bullpen
• Miami- holds the best starting pitching rotation with Henter (best pitcher in the game with a 1.85 ERA), West, and Jarvis; average bullpen led by closer Irving; and weak offense led by Warner
• N.Y. - has a great starting rotation of Carter, Howe, and Cora; an excellent bullpen led by Errico and Fiore; and a starting lineup led by Star that lacks some home run power but hits solidly throughout
• Omaha- has average starting pitching led by Rennor, fair bullpen, and below-average lineup led by Lyonse and Carus
• Philly - boasts the best overall pitching staff with the second best starting rotation with Gantos, Car, and Rush; the best bullpen led by Ellis; and a lineup with a solid middle of the order of Evans, Oko, and Rubin but otherwise average offense
• Texas - has a high hitting offense anchored by Marcus but a very porous pitching staff
• Utah- has one of the best offenses in the game led by Agua and Harlan, featuring a Jekyll and Hyde pitching staff with a strong starting pitching rotation led by Quinta, Lep, and Stava and an inconsistent bullpen led by Bella, one of the best closers in the game, but also features three of the five worst ERAs.

Also noteworthy is the fact that the umpires' names are given, and are as follows:

• PL: Yuk
• 1B: Dum
• 2B: Boo
• 3B: Bum