Alola | Fiore | Galar | Hoenn | Johto | Kalos | Kanto | Kitakami | Orre | Paldea | Sinnoh & Hisui | Unova & Blueberry
Like humans, most Pokémon have a gender, although some of them are genderless (mainly the ones that are animate objects). Many Pokémon are either male or female, and have a percentage rate of how many are male vs female (both are usually at 50%).
In some cases, some Pokémon are exclusively one gender (famously, Nidoran♂ are only male and Nidoran♀ are only female, which is also the case for their respective evolutionary lines). In the games, starting with Generation II, other Pokémon have been classified with a gender (with Nidoran♂ and Nidoran♀ being the only Pokémon to have a gender in the Generation I games).