Orthodoxy is a book by G. K. Chesterton that has become a classic of Christian apologetics. In the book's preface Chesterton states the purpose is to "attempt an explanation, not of whether the Christian faith can be believed, but of how he personally has come to believe it." In it, Chesterton presents an original view of Christian religion. He sees it as the answer to natural human needs, the "answer to a riddle" in his own words, and not simply as an arbitrary truth received from somewhere outside the boundaries of human experience.

G. K. Chesterton was an English writer, poet, philosopher, dramatist, journalist, orator, lay theologian, biographer, and literary and art critic. Chesterton is often referred to as the "prince of paradox". Chesterton is well known for his fictional priest-detective Father Brown, and for his reasoned apologetics.