From Bulbapedia, the community-driven Pokémon encyclopedia.
This is a list of Pokémon by gender ratio.
Most Pokémon are either male or female. However, depending on the species, players are more likely to encounter a Pokémon of a specific gender than the other. Gender plays a vital role in breeding, as offspring inherit the species of the mother and compatible moves from the father. However, Pokémon of either gender can be used if the partner is a Ditto.
Male only
These Pokémon only appear as male. As a result, these Pokémon are incapable of producing offspring of the same species without Ditto or a female counterpart.
Unbreedable
Despite being gendered, these Pokémon cannot breed.
1 ♀ : 7 ♂
These Pokémon normally appear as male, rarely female. This specific gender ratio is used to make it more difficult in breeding more of them since players usually get them as gifts or fossils rather than catch them in the wild. All Starter and Fossil Pokémon are in this group.
Unbreedable
Despite being gendered, these Pokémon cannot breed.
1 ♀ : 3 ♂
These Pokémon usually appear as male, but can be female.
Unbreedable
Despite being gendered, these Pokémon cannot breed.
1 ♀ : 1 ♂
These Pokémon have an equal chance of being either male or female. The vast majority of Pokémon fall under this category.
Unbreedable
Despite being gendered, these Pokémon cannot breed.
3 ♀ : 1 ♂
These Pokémon usually appear as female, but can be male.
Unbreedable
Despite being gendered, these Pokémon cannot breed.
Female only
These Pokémon only appear as female. As a result, they are incapable of passing egg moves to offspring without the help of Ditto or a male counterpart.
Unbreedable
Despite being gendered, these Pokémon cannot breed.
Genderless
Pokémon in these lists aren't assigned a gender. The ones in this list can breed only with Ditto.
Unbreedable
These Pokémon are genderless and cannot breed.