In the summer of 1957 during works on a stone quarry near the village of Murfatlar, Middle Dobrudzha, stone chambers of a medieval monastery from the First Bulgarian Kingdom were found carved in the rock. The monastery was active between the 9th and 11th century AC. Many texts of unknown origin are engraved in its soft limestone walls. It is believed that these scripts were written in an ancient language, called Danube Bulgar, known to have been used by the Bulgars, a Turkic people, who in the 7th century AC established The First Bulgarian Kingdom around the lower parts of the Danube river. However, very little evidence is left of their language. That is why deciphering and understanding of the texts at Murfatlar would significantly improve our knowledge of it. This book is an attempt to study the basics of the Murfaltar writing system: the type of writing (alphabetical, syllabic or logographic); the number of characters in the language and their outlook; connections with other writing systems; time and way of occurrence; deciphering. The study suggests that it is an alphabetical script, with separate characters for vowels and consonants. There are 29 identified characters. The meaning for 25 of these has been discovered (see table 2 on page 128). It was found out that the language most likely originated around the 9th century under the strong influence of the Byzantine Greek alphabet. Tamgas and Bulgarian family and tribal signs were used as a graphic basis. Part of the writings has been successfully deciphered. The assumption that the language of the Danubian Bulgars is Turkic in origin is confirmed, specifically a branch of Turkic referred to as “Bulgar Turkic” or r/l Turkic. The texts are mostly religious and authentically represent Christian terminology in Danube Bulgar. These are probably the oldest Turkic texts with Christian contents. It has also been realized that some characters of the Murfatlar alphabet have served as an archetype for the creation of the letters in the later Cyrillic.