  The current star formation models imply that the binary fraction of
population III stars is non zero. The evolution of such binaries must have led
to formation of compact object binaries. In this paper we estimate the
gravitational wave background originating in such binaries and discuss its
observability. The properties of the population III binaries are investigated
using a binary population synthesis code. We numerically model the background
and we take into account the evolution of eccentric binaries. The gravitational
wave background from population III binaries dominates the spectrum below 100
Hz. If the binary fraction is larger than 0.01 the background will be
detectable by LISA and DECIGO. Gravitational wave background from population
III binaries will dominate the spectrum below 100 Hz. LISA, ET and DECIGO
should either see it easily or, in case of non detection, provide very strong
constraints on the properties of the population III stars.
