Ogham is an ancient Celtic writing system, alphabet, or cipher that was primarily designed to inscript Archaic Irish (sometimes called Primitive Irish), later Old Irish, and some Pictish and Old Welsh. As well as having origins documented in the fields of history, linguistics, and archaeology, it also has a history of magic and mythology in Ancient Celtic Religion or Celtic Paganism. Since the 20th century, there has been a revival of interest in this and other ancient polytheistic religions and spiritual practices by a growing number of Pagan or Neo-Pagan communities across the world. It is the aim of this book to provide the bigger picture about where these symbols have come from, how they have developed, how they have been used, and how their use has evolved over two thousand years.