abstract: This thesis investigates similarities in the diachronic sound changes found in Eastern Old Japanese dialects and in Ryukyuan languages and tests a hypothesis of language contact. I examine three sound changes attested in the Eastern Old Japanese corpus of Kupchik (2011). These three are denasalization of prenasalized obstruents, the fortition of the labial glide [w] and prenasalized / simple voiced fricative [(n)z], and the irregular raising of Eastern Old Japanese mid vowels. Extralinguistic and linguistic evidence is presented in support of a hypothesis for language contact between 8th century Ryukyuan speakers and Eastern Old Japanese speakers. At present, many assumptions bog down any potential evidence of contact. However, cases where reconstructed Ryukyuan could have donated a form into EOJ do exist. With future research into early Ryukyuan development and the lexicons, phonologies, and syntactic patterns of Ryukyuan languages, more can be said about this hypothesis. Alongside testing a hypothesis of language contact, this thesis can also be viewed as an analysis of Eastern Old Japanese spelling variation of the three changes mentioned above. / Dissertation/Thesis / Masters Thesis English 2015