Meowth (Japanese: ニャース Nyarth) is a member of Team Rocket, more specifically part of a trio with Jessie and James, that follows Ash Ketchum and his friends around in the Pokémon anime, usually trying to steal Ash's Pikachu. His major difference from other Meowth, and nearly all other Pokémon, is that he can talk and walk on two legs like a human, and thus, Jessie and James treat him as such. They have never actually "caught" him, which technically makes him a wild Pokémon since he has no Poké Ball of his own; this is unlike Ash's Pikachu, who has a Poké Ball but is never seen travelling in it. Meowth is also the second most prominently-featured Pokémon in the anime, after Pikachu.

In a flashback in Go West Young Meowth, Meowth's earliest memory is being alone at Camp Pokéhearst. With no food, he was always starving and once tipped over a basket of baseballs believing it was food. As punishment for tipping the basket over, the baseball coach hung him from a tree; from this tree, he was able to see a movie called That Darn Meowth!, which depicted a Meowth in Hollywood being given delicious food by its family. Meowth instantly decided to go to Hollywood, which he believed would be a paradise.

However, when he arrived in Hollywood, he was merely perceived as a stray Pokémon, and was constantly being chased for stealing food. Soon, a Meowth gang, led by a Persian, took him in. Meowth lived on the streets as a member of the gang for a long time; the gang annoyed the humans in town by stealing food and causing trouble, the town's local Butcher Shop Owner in particular. One day, Meowth came across a female Meowth named Meowzie. She rejected him, saying that he was poor and that she preferred humans, so Meowth attempted to make himself more human-like to make her love him. Thus, he painstakingly taught himself to speak human language and walk upright like a human. When he approached her after this transformation, she once again rejected him, calling him a freak. Heartbroken, Meowth remembered the first human word he understood—"rocket"—and was inspired to join Team Rocket. Since this incident, Meowth has fallen in love with various cat-like Pokémon, the exception being a Pheromosa, which is a cockroach-like Pokémon.

Meowth has an ambitious, conniving, and idealistic personality. He has made it his life goal to please his boss, Giovanni, and will stop at nothing to capture or steal Pokémon, especially Ash's Pikachu, which he has been pursuing since Pokémon Emergency, the first episode of the anime.

Meowth is a characteristically jealous individual, particularly with other Cat Pokémon, most notably Giovanni's Persian and Matori's own Meowth. He often clashes with them because they are equally as smug and conniving as himself. Many of his personality traits are typical for other Meowth, where they have an affinity for affection, but has an eye for sparkling objects. Unlike most other Pokémon, who are not truly evil and will only commit evil deeds when ordered to do so, as stated by Jessie's Ekans in Island of the Giant Pokémon, Meowth is both perfectly capable of and willing to commit evil deeds without the aid of others. He is motivated by self-interest and greed, but also enjoys the thrill of taking advantage of others.

Despite his seemingly outgoing nature, Meowth also has a contemplative inner side not seen as often. In one of his image songs, Meowth's Song, and in Mewtwo Strikes Back, he is shown to be a bit of a philosopher. In Mewtwo Strikes Back, he and his clone were the only Pokémon not to participate in the giant battle, Meowth remarking in the dub that the originals and the clones shared the same air, moon, and planet, giving them common ground. He noted that if all living beings focused on what was the same among them as opposed to what was different, the world would be a much better place. Meowth comforted Ash's Chimchar in Tears For Fears! and actually expressed some admiration for Ash and his friends. It is possible during that time that Meowth developed a friendship with it, as seen in A Real Rival Rouser! when he, Jessie and James cheered it on, and in Evolving Strategies! when he was happy to see it evolve. On a few occasions, Meowth has become stranded with Pikachu, and during these times, the two work together fairly well. Pikachu distrusts Meowth for obvious reasons, but Meowth is more willing to let go of the past and work together. Usually, by the end of these episodes, Meowth will betray Pikachu once they find Jessie and James.