Ayn Rand was a Russian-American writer and philosopher, and is the favorite author of every libertarian tech bro in Silicon Valley. She's most widely known as the author of The Fountainhead and Atlas Shrugged, and for developing the philosophy of Objectivism.
A staunch anti-communist and free-market capitalist, Rand's Objectivist philosophy declared that the proper moral pursuit of one's own life was one's own happiness. She began preaching Objectivism full time in the 1960s and continued until her death in 1982. Rand is often referred to as a "controversial figure," which is a polite way of saying she wasn't a very nice person. She was pro-colonialism, blatantly racist, and considered homosexuality to be "disgusting" and "immoral." Also, Rand didn't consider herself a feminist and often attacked the ideology of feminism.
Which makes it all the more hilarious that her most famous quote is, in fact, a misquote based on this exchange in The Fountainhead:
“My dear fellow, who will let you?”
“That’s not the point. The point is, who will stop me?”
... and that budding teenage feminists are now wearing it on T-shirts!