  We present the Green-Schwarz action for Type IIA strings on $AdS_4\times
CP^3$. The action is based on a $\Zop_4$ automorphism of the coset
$OSp(4|6)/(SO(1,3)\times SU(3)\times U(1))$. The equations of motion admit a
representation in terms of a Lax connection, showing that the system is
classically integrable.
