Charles Mackay was a Scottish poet, journalist, author, anthologist, novelist, and songwriter, remembered mainly for his book Extraordinary Popular Delusions and the Madness of Crowds.

Extraordinary Popular Delusions and the Madness of Crowds is an early study of crowd psychology by Scottish journalist Charles Mackay, first published in 1841 under the title Memoirs of Extraordinary Popular Delusions. The book was published in three volumes: "National Delusions", "Peculiar Follies", and "Philosophical Delusions". Mackay was an accomplished teller of stories, though he wrote in a journalistic and somewhat sensational style.