  Accretion rates of order 10^-8 M_\odot/yr are observed in young protostars of
approximately a solar mass with evidence of circumstellar disks. The accretion
rate is significantly lower for protostars of smaller mass, approximately
proportional to the second power of the stellar mass, \dot{M}_accr\propto M^2.
The traditional view is that the observed accretion is the consequence of the
angular momentum transport in isolated protostellar disks, controlled by disk
turbulence or self--gravity. However, these processes are not well understood
and the observed protostellar accretion, a fundamental aspect of star
formation, remains an unsolved problem. In this letter we propose the
protostellar accretion rate is controlled by accretion from the large scale gas
distribution in the parent cloud, not by the isolated disk evolution.
Describing this process as Bondi--Hoyle accretion, we obtain accretion rates
comparable to the observed ones. We also reproduce the observed dependence of
the accretion rate on the protostellar mass. These results are based on
realistic values of the ambient gas density and velocity, as inferred from
numerical simulations of star formation in self--gravitating turbulent clouds.
