Catherine ("Cathy") Helen O'Neil is an American mathematician, data scientist, and author.

She is the author of the New York Times best-seller Weapons of Math Destruction, and opinion columns in Bloomberg View.

[5] She worked as an analyst at D. E. Shaw & Co.[6] After becoming disenchanted with the world of finance, O'Neil became involved with the Occupy Wall Street movement,[7][1] participating in its Alternative Banking Group.

[4] A third book, The Shame Machine: Who Profits in the New Age of Humiliation, was published March 2022.

[3][14] In 1993 O'Neil was awarded the Alice T. Schafer Prize from the Association for Women in Mathematics and in 2019 she won the MAA's Euler Book Prize for her book Weapons of Math Destruction.