Rival (Japanese: ライバル Raibaru) is a known trainer class introduced since Generation I. A rival is seen as a important trainer in the video game that can stimulate the player. The player will meet his rival throughout the storyline and will often challenge the player to a Pokémon Battle. The rival of the player can either be a childhood friend of the player, a bully or a hater. A known issue is that the rival always picks a Pokémon that is stronger than the player, for example: The player chooses a grass-type Pokémon, which the rival will pick a fire-type Pokémon. This can be in exception of Dawn and Lucas and also Bianca that are choosing a Pokémon with a type disadvantage. Also some rivals the player also meets also contains to have no one of the three main starter Pokémon, as notable Wally, who captured a Ralts a psychic-type Pokémon. The owner of the main video games of the Pokémon series can also name the rival to whatever he/she wants at the start of the video game or evenly much later in the video game, but it happens mostly before the player obtains his first Gym Badge. The only rivals which name can be given to are: Wally, May, Brendan, Cheren, and Bianca.
Having a main rival has been introduced since Generation I of the Pokémon video game series. The most popular and ongoing rivalry is that between Red and Blue, evenly they have been acknowledge to be true rivals since Generation I and it continues to be like that. The rival of the player mostly appears during the progression of the player's journey which he/she often encounters his/her rival which the player's rival challenging him/her to a Pokémon battle or giving him/her a useful item. A popular issue between rivalries is that the rival mostly picking a Pokémon with the type that is in his advantage, for example: the player chooses a fire-type Pokémon, but his/her rival chooses a water-type Pokémon. In exception of Biance, she chooses a Pokémon with a disadvantaged type than the player, for example: the player chooses Tepig then Bianca will choose Snivy as her starter Pokémon. Also known is that most rivals doesn't have one of the three main primary starters in the video game. Mostly the Pokémon that they have, have been caught or they are befriended with, such as Wally and N, both doesn't have not one of the three starter Pokémon. Wally have captured his Ralts and N is befriended with most of his Pokémon. Most rivals doesn't come to the laboratory to make a choice and picking up their starter Pokémon but to steal one of it, for example: Silver is is looking from the window in the laboratory of Professor Elm, once that Professor Elm didn't pay no any attention to one of his Pokémon, Silver took one of it and fled in a instant. Most rivals has a more deeper story line which is the cause of their strange behavior. Most of the player rivals depends more in good looking Pokémon, strength and strategy.
Pseudo-rival (Japanese: 擬似ライバル Giji Raibaru) is not exactly a rival of the player, it serves more as a helping hand but more competitive to be a better assistant of the Professor instead of depending on the strength of their Pokémon during a Pokémon Battle. Known to be as a helping hand towards the player by giving him/her useful information, giving useful items, and helping him/her out during tag battles. Sometimes they also ask for help if there is a big problem as example: In Pokémon Diamond, Pearl and Emerald, Dawn or Lucas PokéDex has been stolen by a Team Galactic grunt and asked the player for help to get her/his PokéDex back.
Rivals also appears in the anime series of Pokémon for mostly the main characters. The rivals in the anime can be compared to the rivals in the video game but there is a slight difference. Red and Blue counterparts Ash and Gary became friends after a long rivalry while Blue literally shows his hatred to Red after that he defeated him when he was only for a moment a Pokémon Champion. The main characters also learns a lot from their rivals, mostly it happens during their competitions against each other mostly noticing their movements and what they can do for the next time. Known rivalries between characters in the series are:
- Ash has a lot of rivals during his travellings, but his major rivals were: Gary Oak, Paul, Barry, Trip and Bianca. Ash have also a lot of minor rivals in the anime series which they are mostly more in collecting badges and holding friendly competitions which some of them achieved in battling with each other in the Pokémon League.
- Jessie and James both have a rivalry with Butch and Cassidy. Jessie has a major rivalry with Cassidy since childhood, the rivalry between James and Butch can be because of the times that they were assign to capture a red Snorlax.
- May has a rivalry with her fellow co-ordinators Drew, Harley, and Solidad.
- Dawn has a rivalry with her fellow co-ordinators Zoey, Kenny, and Ursula.
- Iris has a rivalry with Georgia, and Cilan has a rivalry with Burgundy.
- Meowth has a rivalry with Giovanni's Persian due that the Persian is Giovanni's favourite something that Meowth dislike because according to his stories he was the former favourite of Giovanni.
There are also rivals that are making their appearance in the manga series of the Pokémon franchise. The rivals in the manga has no difference which can be compared to that of the rivalry that happens in the anime. Known rivals are:
- Satoshi and Shigeru in the Pocket Monsters Zensho manga.
- Hiori and Rocco in the Phantom Thief Pokémon 7 manga.
- Red and Blue, Gold and Silver, Crystal and Eusine, Ruby and Sapphire and, Team Magma and Team Aqua in the Pokémon Adventures manga.
- Hareta, Jun and Koya, and Mitsumi has Jupiter in the Pokémon Diamond & Pearl Adventure! manga.
- Gold and Black in the Pokémon Gold & Silver: The Golden Boys manga.
- Red, Green and Blue in the Pokémon Pocket Monsters manga.
- Ryouga and Hariru in the Pokémon RéBURST manga.
- Normally, N doesn't count as being a rival of the player. Due to that N became more involved in the plans of Team Plasma and the constant meeting between him and player he has been considered as the main rival of the player.
- Red and Blue still has a bitter rivalry known that Blue still despise him by the fact that Red defeated him while he was the Pokémon Champion only for a moment.
- Brendan and May are the only rivals that can be chosen as main characters.
- Mostly known, rivals are mostly the player childhood friend or also living in the same town or city. Silver and Wally are both rivals of the player but they are not a childhood friend of the player or evenly coming from the same town or city.