The invention Johannes Gutenberg popularized in the 15th century was the printing press, specifically the movable type printing press. Invented around 1440, Gutenberg's press revolutionized the production of books and written materials. This innovation drastically reduced the cost of printing, making literature more accessible to the masses and facilitating the spread of knowledge and ideas. It played a crucial role in the Renaissance, the Reformation, and the advancement of education, ultimately shaping the course of Western civilization.