  The ``Little Higgs'' opens up a new avenue for natural electroweak symmetry
breaking in which the standard model Higgs particle is realized as a
pseudo-Goldstone boson and thus is generically light. The symmetry breaking
structure of the Little Higgs models predicts a large multiplet of
(pseudo-)Goldstone bosons and their low energy interactions below the
ultraviolet (UV) completion scale $\Lambda \sim 4\pi f \sim O(10)$ TeV, where
$f$ is the Goldstone decay constant. We study unitarity of the Little Higgs
models by systematically analyzing the high energy scatterings of these
(pseudo-)Goldstone bosons. We reveal that the collective effect of the
Goldstone scatterings via coupled channel analysis tends to push the unitarity
violation scale $\Lambda_U$ significantly below the conventional UV scale
$\Lambda \sim 4\pi f$ as estimated by naive dimensional analysis (NDA).
Specifically, $\Lambda_U \sim (3-4)f$, lying in the multi-TeV range for $f\sim
1$ TeV. We interpret this as an encouraging sign that the upcoming LHC may
explore aspects of Little Higgs UV completions, and we discuss some potential
signatures. The meanings of the two estimated UV scales $\Lambda_U$ (from
unitarity violation) and $\Lambda$ (from NDA) together with their implications
for an effective field theory analysis of the Little Higgs models are also
discussed.
