It's a trap!

why is Saber a female in the first place? Isn't she suppose to be KING (implicitly, male) Arthur?

Just as a wild guess, he knew it when he wrote the character and has a reason for it.

I'm guessing there's some sexist or something going on...who knows. Maybe the writer thought that when a person pulls the sword from the stone they become King...not Queen, so who knows. As for the picture I really like the decal on Saber's shirt. Its quite funny actually.

Artist's website: http://www.puyotopia.com/

comment #6071

She is a king. The king of knight and I doubt there would have been so much interest in FS/N if it was like this: post #59268!

She is a king. But in fate stay night shes arthuria pendragon. Shes a woman disgused as a man since no one would take a female leader seriously. I think it mentions that in the game somewhere lol

She used magic to hide her ponos, or something. She also had a son, somehow.

The real answer is: Takeuchi REALLY wanted to draw a woman in armor, combined with the reality that they'd have to make an entirely new audience to play a game with a woman protaganist convinced Naasu to write saber as a woman.

Actually in the original idea Saber was a male with Archer-like personality:
post #459507
And his Master, the main heroine a glasses-girl mage.
post #220735
Though I am uncertain how much she resembled Rin.
Anyways as FSN became a VN and and so an eroge it was natural to switch the genders...and actually many other things. You can't imagine how many weird ideas they had. Actually even I can't.:)