The purpose of this thesis is to provide a grammatical sketch of Loup A, a long-extinct Eastern Algonquian language surviving primarily in the field notes of the Sulpician missionary Jean-Claude Mathevet. These field notes were edited and annotated by Gordon Day (1975); this edition provides the sole source of original linguistic data. This grammatical sketch includes a chapter on phonetics and phonology, from a decidedly historical point of view, as well as brief sections on syntax and derivation, although the main focus is to attempt to account for all inflected forms found in the field notes. As well, this thesis identifies the Loup of Mathevet's field notes as the Nipmuck tribe of central Massachusetts. The above areas of study provide as complete a grammatical sketch as one could expect given the li ited data available, but one that is more than adequate as a concise reference to the structure of an Algonquian language that has until now been almost entirely unexplored.