Mario is depicted as a short, pudgy, Italian American plumber who lives in the Mushroom Kingdom. He repeatedly stops the turtle-like Bowser's numerous plans to kidnap Princess Peach and subjugate the Mushroom Kingdom. He also has other enemies and rivals, including Donkey Kong and Wario. Since 1995, Mario has been voiced by Charles Martinet.

As Nintendo's mascot, Mario is arguably the most famous character in video game history, and his image is commonly associated with video games. Mario games, as a whole, have sold more than 210 million units, making the Mario series the best-selling video game series of all time. Outside platform games, he has appeared in video games of other genres, including the Mario Kart racing series, sports games, such as the Mario Tennis and Mario Golf series, and role-playing games such as Paper Mario and Super Mario RPG. He has also inspired television shows, film, comics, and a line of licensed merchandise.

Mario was created by Shigeru Miyamoto in his attempts to produce a best-selling video game for Nintendo, after previous titles, such as Sheriff, had not achieved the same success as other titles such as Pac-Man. Originally, Miyamoto wanted to create a video game that used the characters Popeye, Bluto, and Olive Oyl. At the time, however, Miyamoto was unable to acquire a license to use the characters (and would not until 1982), and ended up making Jumpman (later known as Mario), Donkey Kong, and Pauline. In the early stages of the game, Mario was unable to jump, and the focus was to escape a maze. However, Miyamoto added in that ability, saying "If you had a barrel rolling towards you, what would you do?".

Mario's name was originally "Mr. Video", and he was to be used in every video game Miyamoto developed. This idea was inspired by manga artists such as Osamu Tezuka and Fujio Akatsuka, who feature several characters across multiple manga, as well as British director Alfred Hitchcock, who appears in most of his own films. During localization of the game for American audiences, Nintendo of America's warehouse landlord Mario Segale confronted its then-president Minoru Arakawa, demanding back rent. Following a heated argument in which the Nintendo employees eventually convinced Segale he would be paid, they opted to name the character in the game Mario after him. Miyamoto commenting that if he had named him Mr. Video, he likely would have "disappeared off the face of the Earth". Mario's profession was chosen to be carpenter in an effort to reflect that as a character he was an ordinary hard worker; the profession was also intended to make it easier for players to identify with the character. After a colleague suggested that Mario more resembled a plumber, Miyamoto changed his profession accordingly and developed Mario Bros., featuring the character in the sewers of New York City.

Due to the graphical limitations of arcade hardware at the time, Miyamoto clothed the character in bright red overalls and a blue shirt to contrast against each other and the background. A cap was added to let Miyamoto avoid drawing the character's hairstyle, as well as to circumvent issues involved with animating his hair as he jumped. To make him appear human onscreen despite his small size Mario was given a large nose and a mustache to avoid drawing a mouth due to the difficulty of illustrating facial expressions at that size. Miyamoto has stated that it was the addition of the mustache which led him and his team to decide on Mario being Italian stating their reaction as being like "Oh, he’s got a mustache. Well, let’s make him Italian."

Miyamoto developed Mario with the idea of using him as a "go to" character that could be put in any title as needed, albeit in cameo appearances as at the time he was not expecting Mario to become popular. To this end he originally called the character "Mr. Video", comparing his intent to have Mario appear in later games to the cameos done by Alfred Hitchcock within his films. Over time, Mario's appearance has become more defined; both a red "M" in a white circle on the front of his hat and gold buttons on his overalls have been added. Miyamoto attributed this process to the different development teams and artists for each game as well as advances in technology as time has gone on. Nintendo has never revealed Mario's full name, stating only that it was not "Mario Mario" despite the implication of the Mario Bros. series' title, its use in the film, and information given in the Prima official Guidebook to Mario and Luigi: Superstar Saga.

Mario debuted as "Jumpman" in the arcade game Donkey Kong in 1981. He is shown as a carpenter that has a pet ape. The carpenter mistreats the ape, so Donkey Kong escapes and kidnaps Jumpman's girlfriend, originally known as the Lady, but later named Pauline. The player must take the role of Jumpman and rescue the girl. He was first named "Mario" in the arcade game Donkey Kong Junior in 1982, the only game in which he has ever been portrayed as an antagonist. In the 1983 arcade game Mario Bros. Mario and his younger brother Luigi are portrayed as Italian-American plumbers, who have to defeat creatures that have been coming from the sewers below New York. Their surname was "Mario", resulting in Mario's full name being first given here as "Mario Mario".

In Super Mario Bros. for the Nintendo Entertainment System (NES), Mario saves Princess Toadstool (later known as Princess Peach) of the Mushroom Kingdom from King Koopa. To save Princess Toadstool, Mario conquers the eight worlds of the Mushroom Kingdom by going to the castle in each to defeat a minion of King Koopa. To reach each castle, Mario battles through three "sub-worlds" by defeating or avoiding King Koopa's henchmen. If Mario successfully fights his way through the castle and defeats the minion, a Mushroom Retainer is freed. Inside the eighth castle, Mario has a final fight with King Koopa and frees Princess Toadstool. Later, in Super Mario Bros. 2, the player could choose between Mario and his friends Luigi, Toad, or Princess Peach. Each character possesses unique abilities, with Mario being the most well-rounded. In Super Mario Bros. 3 Mario embarks on a quest to save the rulers of seven kingdoms from Bowser and his children, the Koopalings and travel across eight worlds to restore order to the Mushroom World and rescue Princess Peach. Mario is introduced to new power-ups that augment his abilities.

In Super Mario Land an alien named Tatanga appears, hypnotizes the inhabitants of an area called Sarasaland, and kidnaps their ruler, Princess Daisy. Mario then sets out to rescue her from Tatanga, traveling through the four geographical areas of Sarasaland and defeating Tatanga's minions along the way. He finally corners Tatanga in the skies of the Chai kingdom, bringing down his alien warship and rescuing Daisy.

In Super Mario World, Mario and Luigi are taking Princess Peach for a vacation in Dinosaur World sometime after the events of Super Mario Bros. 3 when Peach is kidnapped by Bowser. Mario and Luigi are introduced to the Yoshis, dinosaurs that live in Dinosaur World, and they help rescue Peach by allowing Mario and Luigi to ride them. In Super Mario Land 2: 6 Golden Coins, which takes place immediately after the original Super Mario Land, Mario's evil counterpart Wario has put an evil spell over Mario Land while Mario was away in Sarasaland, renaming the area Wario Land. The inhabitants are now brainwashed into thinking that Wario is their master and Mario is their enemy. Wario's motive behind this sudden attack was to take control over Mario's castle in order to have a palace of his own. To stop Wario, Mario finds the 6 Golden Coins throughout Mario Land and regains access to his castle. In Super Mario World 2: Yoshi's Island, a stork carries Baby Mario and Baby Luigi across the sea, but the evil Magikoopa Kamek emerges and steals Baby Luigi, and Baby Mario falls onto an island in the middle of the sea called Yoshi's Island, home to Yoshis. He lands on a green Yoshi, and he and the rest of the Yoshis journey through the game's six worlds to rescue Baby Luigi and the stork back from Baby Bowser and Kamek.