The research, entitled Diglossia of Javanese and Sundanese Languages in Language Society in Bengbulang Village, Karangpucung Sub-district, Cilacap Regency, aims to determine the types and forms of language diglossia that exist in the speech of the language community in Bengbulang Village. Based on these objectives, the type of research used in this study includes qualitative descriptive research. The method used in this study is translated into steps according to the stages of implementation, namely (1) describing the problems that exist in the research, (2) collecting data sources related to research, and (3) analyzing data. Th. e data in this study are in the form of citizen speech or language communities indicated by the use of diglossia in it. This study's data sources, namely the results of speech recordings used by the community. This study is included in the type of qualitative research or rather an analytical descriptive because this study aims to describe the diglossia phenomenon that occurs during the language community, especially in Bengbulang Village as a transitional or border-area community. The language communities in Bengbulang Village, Karangpucung Sub-district, Cilacap Regency are divided into two categories or groups, namely (a) bilingual and diglossic language communities and (b) diglossic language communities without bilingualism. The factors that cause diglossia are (a) geography, (b) education, (c) marriage, and (d) dialect differences.