Biohazard CODE: Veronica, commonly abbreviated RECV) is the fourth game in Capcom's Resident Evil survival horror series originally released for the Sega Dreamcast in 2000. It is notable for being the first Resident Evil title to debut on a non-Sony platform, as opposed to the first three installments, which were originally PlayStation games before being ported to other platforms.

An updated version of the game titled Code: Veronica X (Complete Edition) was released for the Dreamcast (Japan only) and PlayStation 2 in 2001 and the GameCube in 2003. This new version includes new cut scenes spliced into the main game and mild graphical changes.

It was the first game in the series made for a sixth generation console, and also the first core title in the series to use full polygonal environments over the static, pre-rendered backgrounds that characterized the series.

Code: Veronica is the first Resident Evil game in the main series to use 3D backgrounds instead of the traditional pre-rendered ones. Despite this, the camera does not follow the player around, but swings between semi-fixed angles (similar to the original Dino Crisis). However, two weapons in the game (a sniper rifle and a linear launcher) can be fired from the character's point of view and a first person view mode is available in the game's unlockable "Battle Mode" minigame.

Gameplay remained largely unchanged from Resident Evil 2, although features from Resident Evil 3: Nemesis (which was developed in tandem with Code: Veronica) such as explosive oil drums and a 180-degree turn carried over to this game. Items from Resident Evil 2, such as upgradeable handgun parts and "side packs" for larger item capacity are featured, as well as new weapons such as crossbow arrows mixed with gun powder and Anti-B.O.W. rounds for the grenade launcher. A unique feature of Code: Veronica is the inclusion of various dual wielding pistols, allowing the player to target two enemies at the same time. Some of the more subtle improvements in Code: Veronica includes the addition of continues, allowing the player to retry a scene after a game over, and the ability to pick and use a healing herb when the character's inventory is full.

As with previous installments, Code: Veronica features two protagonists. This time they are Claire Redfield and her brother Chris. Unlike Resident Evil 2, in which the player could choose to start the game with either character, Code: Veronica forces players to take control of Claire for the first half of the game and then start the second half with Chris. All of Claire's weapons and items left in the item box are available for Chris to pick up in his half of the game. In addition, a third character, Steve Burnside, is briefly playable during Claire's half of the game and Claire herself is playable during a short portion of Chris' half of the game.

Like previous Resident Evil titles, there are hidden features that are unlocked after meeting certain requirements. After completing the main game, a "Battle Game" is unlocked in which the player can choose from one of five characters (Chris, Claire, two unlockable characters, Albert Wesker and Steve Burnside, and an alternate version of Claire)and travel through a series of rooms and clear each area of monsters and eventually defeat a character-specific boss in the quickest time possible. Both the main game and the "Battle Game" feature their respective unlockable weapons.

The game is set three months following the events depicted in Resident Evil 2 and Resident Evil 3: Nemesis. The plot moves away from Raccoon City and onto Rockfort Island, a solitary private isle owned by the Umbrella Corporation, although much of the later portions of the game takes place in an Umbrella-owned transport terminal in Antarctica. Rockfort Island houses several facilities including a prison, a military training base, the Ashford family's palace, a private residence and an airport. The Antarctic transport terminal at the end of the game includes several facilities and a residence, including a replica of the lobby of the Spencer Mansion from the original Resident Evil.

The game begins with heroine Claire Redfield raiding one of the Umbrella Corporation's facilities in Paris. She is captured and imprisoned on Rockfort Island. The island is contaminated by the monster-creating T-Virus. Claire escapes and teams up with inmate Steve Burnside. They eventually escape via plane, but it crashes into the Antarctica facility. There they encounter old and new enemies as they try to survive.

Claire's brother, Chris arrives on Rockfort in search of her. He learns Claire is long gone and that old enemies are alive and well. Chris eventually finds his way to Antarctica where he is reunited with Claire. Steve is killed in battle and Chris and Claire barely escape a gigantic explosion in a stolen jet.