Helen Jackson in Son of Ingagi (1941)
Nobody seems to have mentioned Virginia Lee, from Skin Horse. Black Hair.
The same comic strip also has Tigerlily Jones, who is African American and has a very mod afro.
…You, sir or madam, have just won the internet. Or at least my tiny portion of it. Even I didn’t think of that and I freaking adore that character.
“Opps.”
However, it has come to my attention that some various characters are missing.
Winifred Burkle; aka “Fred” from Angel. Not a villain, but definitely a scientist and could be labeled as “mad” with a fair degree of accuracy.
Lady Octopus; aka Carolyn Trainer, from comics.
Madame Olivier from The Big Four by Agatha Christie. It was published in 1927, so it’s a bit old…
Maria Trovaya, in one of the many alternate universes of the Marvel Comics, I believe. She was the first wife of Dr. Henry “Hank” Pym and was thought dead, but he found her alive, albeit with her brain enlarged to ridiculous sizes. It could be virtually guaranteed that she had little grasp on sanity with the amount of cognitive ability that had been forced upon her.
And finally, probably the most insane of the lot, Dr. Emily Grey, from Red vs. Blue, Seasons 12 and 13. She be cwazy mad off da hook, yo. Like…whoo-woo. spirals finger by his head.
So. Yeah.
I would consider Root more of a mad IT specialist. She could have a doctorate though.
Without looking at anyone else’s answers…
Washu Hakubi
Agnes Heterodyne
Gadget Hackwrench
Hedy Lamarr
Marie Curie
Hard list to make…and I’m not sure they all count.
Well, there’s me. I’m plotting the slow painful deaths of a couple co-workers right now. They totally deserve it, in case you are concerned. Once poisoned a couple of my staff a little bit, although that was an accident. Also a bit ticked at my husband for leaving me the dinner dishes again.
Dr. Harleen Quinzel, better known as Joker’s sidekick, Harley Quinn.
Agatha Heterodyne
Yzma from *The Emperor’s New Groove. *
I wouldn’t call Ivy a mad scientist - she is a scientist, and she is mad, but she doesn’t really engage in mad science as a rule - she did in her current origin, and the occasional story involves her breeding a new and dangerous plant, or synthesizing a new toxin, but mostly it’s the plant control or her internally created toxins (and mind control substances) that result from past mad science.
Actually, looking through the thread more (probably should have done that first) a lot of the suggestions have the same failing. There is a significant difference between ‘a scientist who is mad’ and ‘a Mad Scientist’, which I think the link in the OP spells out pretty well.
Only one I can think of is Franny K Stein
Nobody’s yet mentioned the first one that sprang to my mind - Dr Hilda Landstrom from Red Dwarf (“Quarantine”)
Not a long-lasting character but quite, quite mad.
What’s dead, and dead, and dead all over? Yooooouuuu!