"The Age of Reason" was a series of influential pamphlets written by Thomas Paine throughout the 1790s and into the early 1800s. The three-part work, published in 1794, 1795, and 1807, was officially called "The Age of Reason; Being an Investigation of True and Fabulous Theology", but it is commonly just referred to as "The Age of Reason".

The work was an attack on orthodox Christianity. Paine, who was a deist, advanced the notion that God existed but insisted supernatural occurrences in the Bible were nothing but myths. In "The Age of Reason", he also attacked the Church as being corrupt and too institutionalised. This work received a mixed reception but was nevertheless important in promoting deism as an alternative to traditional Christianity.