The NWChemEx project is redesigning and reimplementing NWChem for pre-exascale and exascale computers. NWChemEx is based on NWChem, an open-source, high-performance parallel computational chemistry code funded by the DOE Biological and Environmental Research (BER) program that provides a broad range of capabilities for modeling molecular systems. NWChemEx will support a broad range of chemistry research important to DOE BER and DOE Basic Energy Sciences on computing systems that range from terascale workstations and petascale servers to exascale computers.