Does this seem to fall under the definition of delusion?

[Anonymous]

A person born in a male body thinking they are a girl or a person born in a female body thinking they are a boy

The definition of delusion is

a false belief or judgment about external reality, held despite incontrovertible evidence to the contrary, occurring especially in mental conditions.

[Anonymous]

I'm not a psychologist but you have to realize the concept boy and girl are largely made up. Scientifically, the main thing we can say is, boy means to have a penis. However, you and I both know that isn't all there is to being a boy. Boy represents things that are not scientific too and maybe even more so.

You cannot dismiss inner reality.

[Lliam]

Completely delusional. Rather psychotic. It's like a person believing that they are Napoleon Bonaparte or Joan of Arc. It's one thing to identify and quite another to believe.
And, according to the APA Handbook, gender dysphoria is a mental illness.