A generalized Lagrangian mechanics is a triple ΣGL=(M,E,Fe) formed by a real n-dimensional manifold M, the generalized kinetic energy E and the external forces Fe. The Lagrange equations (or fundamental equations) can be defined for a generalized Lagrangian mechanical system ΣGL. We get a straightforward extension of the notions of Riemannian, or Finslerian, or Lagrangian mechanical systems studied in the recent book [7]. The applications of this systems in Mechanics, Physical Fields or Relativistic Optics are pointed out. Much more information can be found in the books or papers from References [1–10].