  The Fulde-Ferrell-Larkin-Ovchinnikov (FFLO) phase was first predicted in 2D
superconductors about 50 years ago, but so far unambiguous experimental
evidences are still lacked. The recently experimentally realized
spin-imbalanced Fermi gases may potentially unveil this elusive state, but
require very stringent experimental conditions. In this Letter, we show that
FFLO phases may be observed even in a 3D degenerate Fermi gas with spin-orbit
coupling and in-plane Zeeman field. The FFLO phase is driven by the interplay
between asymmetry of Fermi surface and superfluid order, instead of the
interplay between magnetic and superconducting order in solid materials. The
predicted FFLO phase exists in a giant parameter region, possesses a stable
long-range superfluid order due to the 3D geometry, and can be observed with
experimentally already achieved temperature ($T\sim 0.05E_{F}$), thus opens a
new fascinating avenue for exploring FFLO physics.
