St. Lawrence Island / Central Siberian Yupik is an endangered language, indigenous to St. Lawrence Island in Alaska and the Chukotka Peninsula of Russia, that exhibits pervasive agglutinative and polysynthetic properties. This paper discusses an implementation of a finite-state morphological analyzer for Yupik that was developed in accordance with the grammatical standards and phenomena documented in Steven A. Jacobson’s 2001 reference grammar for Yupik. The analyzer was written in foma, an open source framework for constructing finite-state grammars of morphology. The approach presented here cyclically interweaves morphology and phonology to account for the language’s intricate morphophonological system, an approach that may be applicable to languages of matching typology. The morphological analyzer has been designed to serve as foundational resource that will eventually underpin a suite of computational tools for Yupik to assist in the process of linguistic documentation and revitalization.