Victoria Hart, commonly known as Vi Hart, is a self-described "recreational mathemusician" who is most known for her mathematical videos on YouTube.
I copied the previous text from Wikipedia but the next few lines of text would not be from wikipedia.
Vi Hart one of the well know youtube users with 795,249 subscriptions. She's known for her interesting videos which mainly contains elements of mathematics. She can sing too!
Though you should not think of her as being deemed as a mathematician just because of her youtube channel, she has co-authored several research papers on computational geometry and mathematics of paper folding .
Her videos always motivated me to stay with maths. From the first video of Doodling in Math Class (that I saw for the first time) to her Snail videos or Mobeus Strip story. She is a GENIUS!