Wii Fit is a 2007 exergaming video game developed and published by Nintendo for the Wii. It features a variety of yoga, strength training, aerobics, and balance mini-games for use with the Wii Balance Board peripheral. Designer Hiroshi Matsunaga described the game as a "way to help get families exercising together". It has since been adopted by various health clubs around the world, and has previously been used for physiotherapy rehabilitation in children and in nursing homes to improve posture in the elderly.

The game has received generally positive to mixed reviews, despite criticism over the lack of intensity in some of its workout activities. As of March 2022^[update], Wii Fit was the third best selling console game not to be packaged with a console, having sold 22.67 million copies.

Wii Fit Plus, an enhanced version featuring additional games, activities, and features, was released for the Wii in October 2009. It also garnered positive reception and was a commercial success; as of March 2022^[update], it is the seventh best-selling game on the Wii, with a total of 21.13 million copies sold. Both versions have sold a combined total of 43.8 million copies, making the game one of the best-selling video games of all time.

Wii Fit requires the use of the Wii Balance Board, a unique platform peripheral that the player stands upon during play. The Wii Balance Board can detect and track the user's center of balance (COB), a feature heavily used in the game; it will also measure weight in the same way as a bathroom scale. Wii Fit contains more than 40 activities designed to engage the player in physical exercise, which consist of yoga poses, strength training, aerobics, and balance games. Most activities generally focus on maintaining COB and improving posture.

Players register and play in Wii Fit via a user profile, assigned with the player's date of birth, height, and Mii character, that keeps track of the player's progress. Physical activities done outside of Wii Fit can also be logged into the profile. Wii Fit allows up to eight different profiles to be registered.

The Yoga and Strength Training activities in Wii Fit provide the player with an on-screen personal trainer who offers direction and evaluation. While standing or otherwise leaning on the Wii Balance Board, the player is instructed to perform the activity by precisely imitating the trainer's actions. In Yoga, the player holds a particular pose or series of poses for a duration of time; while in Strength Training the player performs a set number of repetitions of the exercise selected. During these sessions, the player is shown a visual indication of their COB, represented as a red dot. The trainer advises the player to maintain the COB throughout the activity, requesting that it not move outside a particular threshold usually indicated as a yellow circle. When the activity ends, the player is scored based on how well the player kept their balance during the session: points are deducted if the player's body haphazardly swayed or shook at any point. Wii Fit has 30 Yoga and Strength Training activities.

The other two major categories in Wii Fit, Aerobics and Balance Games, consist of 18 minigame activities that feature Miis as playable characters. Aerobics focus on activities that require more vigorous movement, and are divided into three distinct types: hula hooping, step aerobics, and jogging. In Hula Hoop, the player twirls their hips in order to spin a series of hoops, and is scored on the number of spins achieved within a period of time. Step aerobics (simply referred to as "Step" in-game) focus on stepping on and off the Wii Balance Board in a rhythmic fashion. In jogging, which does not use the Wii Balance Board, the player runs in place while keeping the connected Wii Remote in their pocket, which acts as a pseudo-pedometer. The game provides variations of step aerobics and jogging (called "Free Step" and "Free Run" respectively) where the user may exercise at their own pace and does not require viewing the game screen; the player is able to watch television or something similar while performing the exercise. Balance Games consist of nine activities that focus on directly controlling the game using the player's COB. "Soccer Heading", for example, focuses on leaning left or right to control the player's Mii in order to head incoming soccer balls. Another, "Table Tilt", focuses on directing balls into holes by shifting the player's balance to tilt the platform they rest on. Activities based on slalom skiing, snowboarding, and tightrope walking are also available, and a Zazen-based game (called "Lotus Focus") in which the player sits on the Wii Balance Board and remains motionless for a period of time.

Players may undergo "Body Tests", in which the player's body mass index (BMI) is calculated and balance control is tested. Each Body Test determines and updates the player's "Wii Fit Age", which loosely suggests the player's physical strength in relation to their true age. A standalone application called "Wii Fit Channel" may be installed to the Wii Menu in order for players to perform Body Tests without needing to load the Wii Fit game disc.