The Lattice package is a Maple package to design and analyze charged-particle beam lines and circular machines. It employs a beam-line description using the standard elements (dipoles, quadrupoles and so on) and retains the algebraic power of Maple. Beam-line elements are described using the equations governing the particle motion in algebraic form. In this way it is possible to compute expressions for beam-line parameters like Twiss functions, dispersion and such, for beam lines or rings, and to perform analysis on these expressions using the full power of Maple.