Infinite-dimensional Lie Groups: General Theory and Main Examples provides a comprehensive introduction to this important subject, examining the structure theory of infinite-dimensional Lie groups by developing a broad framework of Lie theory and illustrating the general results through a detailed discussion of the major classes of Lie groups. Together with its companion volume subtitled, Geometry and Topology, these essentially self-contained texts provide all necessary background as regards generally locally convex spaces, finite-dimensional Lie theory and differential geometry, with modest prerequisites limited to a basic knowledge of abstract algebra, point set topology, differentiable manifolds, and functional analysis in Banach spaces. The clear exposition includes careful explanations, illustrative examples, numerous exercises, and detailed cross-references to simplify a non-linear reading of the material.