  In this contribution I summarize our current knowledge of the nature and
significance of starburst-driven galactic winds (``superwinds''). Superwinds
are complex multiphase outflows of cool, warm, and hot gas, dust, and
magnetized relativistic plasma. The observational manifestations of superwinds
result from the hydrodynamical interaction between the primary energy-carrying
wind fluid and the ambient interstellar medium. Superwinds are ubiquitous in
galaxies in which the global star-formation rate per unit area exceeds roughly
10$^{-1}$ M$_{\odot}$ yr$^{-1}$ kpc$^{-2}$. This criterion is met by local
starbursts and the high-z Lyman Break galaxies. Several independent datasets
and techniques imply that the total mass and energy outflow rates in a
superwind are comparable to the starburst's star-formation-rate and mechanical
energy injection rate, respectively. Outflow speeds in interstellar matter
entrained in the wind range from $\sim 10^2$ to $10^3$ km/s, but the primary
wind fluid itself may reach velocities as high as $\sim$3000 km s$^{-1}$. The
available X-ray and far-UV ($FUSE$) data imply that radiative losses in
superwinds are not significant. Superwinds may have established the
mass-metallicity relation in ellipticals and bulges, polluted the present-day
inter-galactic medium to a metallicity of $\sim$ 10 to 30% solar, heated the
inter-galactic medium, and ejected enough dust into the inter-galactic medium
to have potentially observable consequences.
