What kind of Bergamot is used in Earl Grey tea?

The Bergamot used in Earl Grey tea is the fruit of the bergamot orange tree, which is a citrus hybrid. It's not a true "bergamot" in the botanical sense, but rather a specific type of orange.

To be more precise, the bergamot orange is a hybrid between a bitter orange and a lemon (Citrus aurantium × Citrus limon).

While the term "bergamot" can sometimes refer to other plants, the one used in Earl Grey tea is exclusively the bergamot orange, scientifically known as Citrus bergamia.