The Collaborative International Dictionary of English v.0.48:

Mandatary \Man"da*ta*ry\, n. [L. mandatarius, fr. mandatum a
   charge, commission, order: cf. F. mandataire. See Mandate.]
   1. One to whom a command or charge is given; hence,
      specifically, a person to whom the pope has, by his
      prerogative, given a mandate or order for his benefice.
      --Ayliffe.
      [1913 Webster]

   2. (Law) One who undertakes to discharge a specific business
      commission; a mandatory. --Wharton.
      [1913 Webster]

WordNet (r) 3.0 (2006):

mandatary
    n 1: the recipient of a mandate [syn: mandatary, mandatory]