  (ABBREVIATED) Understanding the formation of stars in galaxies is central to
much of modern astrophysics. In this review the relation between interstellar
turbulence and star formation is discussed. Supersonic turbulence can provide
support against gravitational collapse on global scales, while at the same time
it produces localized density enhancements that allow for collapse on small
scales. The efficiency and timescale of stellar birth in Galactic gas clouds
strongly depend on the properties of the interstellar turbulent velocity field,
with slow, inefficient, isolated star formation being a hallmark of turbulent
support, and fast, efficient, clustered star formation occurring in its
absence. Star formation on scales of galaxies as a whole is expected to be
controlled by the balance between gravity andturbulence, just like star
formation on scales of individual interstellar gas clouds, but may be modulated
by additional effects like cooling and differential rotation. The dominant
mechanism for driving interstellar turbulence in star-forming regions of
galactic disks appears to be supernovae explosions. In the outer disk of our
Milky Way or in low-surface brightness galaxies the coupling of rotation to the
gas through magnetic fields or gravity may become important.
