We present a complete formalization of Persian inflectional morphology using a unification-based framework. The morphological analyzer was developed for use in a Persian-English machine translation system; it computes the part of speech categories and returns all syntactically relevant inflectional features for a word. The morphological analyses are represented as feature structures, which can easily be used by a syntactic parser. The morphological formalism consists of a declarative description of rules utilizing typed feature structures. Persian morphotactics include a few prefixes and sequences of suffixes with cooccurrence constraints between non-adjacent morphemes. The verbal inflectional morphology is rich and is characterized by a complex system of conjugations. A morphological rule associates a regular expression describing a set of character strings to a typed feature structure. Rules can be combined using regular expression operators and they can be factorized in conjugation tables. The morphological engine is implemented as a finite-state transducer where the left projection is the input string and the right projection is a typed feature structure.