This article reviews the Little Higgs models of electroweak symmetry breaking
and their phenomenology. Little Higgs models incorporate a light composite
Higgs boson and remain perturbative until a scale of order 10 TeV, as required
by precision electroweak data. The collective symmetry breaking mechanism,
which forms the basis of Little Higgs models, is introduced. An explicit, fully
realistic implementation of this mechanism, the Littlest Higgs model, is then
discussed in some detail. Several other implementations, including simple group
models and models with T parity, are also reviewed. Precision electroweak
constraints on a variety of Little Higgs models are summarized. If a Little
Higgs model is realized in nature, the predicted new particles should be
observable at the Large Hadron Collider (LHC). The expected signatures, as well
as the experimental sensitivities and the possible strategies for confirming
the Little Higgs origin of new particles, are discussed. Finally, several other
related topics are briefly reviewed, including the ultraviolet completions of
Little Higgs models, as well as the implications of these models for flavor
physics and cosmology.Comment: 60 pages, 17 figures. Invited review article submitted to Progress of
Particle and Nuclear Physic