Pi Beta Phi (ΠΒΦ), often known simply as Pi Phi, is an international women's fraternity founded at Monmouth College, in Monmouth, Illinois, on April 28, 1867, as I. C. Sorosis, the first national secret college society of women to be modeled after men's Greek-letter fraternities. It is sometimes referred to by its original designation, a women's fraternity, as it was founded before the term "sorority" was coined.