Old men are my favorite feminists. Terry Pratchett is an excellent example. In fact, he is an exemplar.
Monstrous Regiment is about a barmaid named Polly who dresses like a boy to go looking for her brother. After she enlists as a soldier, she discovers that she’s not the only crossdresser in her unit, but she can’t figure out who the voice in the darkness is…
This is one of his later books, so the plot holds together quite well. Interestingly, Pratchett’s overall quality has improved tremendously over time, but even the early books portray female characters convincingly. Even more interestingly, he’s incredibly nuanced about the social dynamics of all-male gatherings, all-female gatherings, and mixed company.
My favorite bit of Monstrous Regiment was this footnote: “A woman always has half an onion left over, no matter what the size of the onion, the dish, or the woman.”