  We propose an experimentally feasible scheme to generate
Greenberger-Horne-Zeilinger (GHZ) type of maximal entanglement between many
atomic ensembles based on laser manipulation and single-photon detection. The
scheme, with inherent fault tolerance to the dominant noise and efficient
scaling of the efficiency with the number of ensembles, allows to maximally
entangle many atomic ensemble within the reach of current technology. Such a
maximum entanglement of many ensembles has wide applications in demonstration
of quantum nonlocality, high-precision spectroscopy, and quantum information
processing.
