The Atacama Large Millimeter/submillimeter Array (ALMA) is an international radio telescope under construction in
the Atacama Desert of northern Chile. ALMA will be situated on a high-altitude site at 5000 m elevation, allowing
excellent atmospheric transmission over the instrument wavelength range of 0.3 to 3 mm. ALMA will contain an array
of up to sixty-four 12-m diameter high-precision antennas arranged in multiple configurations ranging in size from 150
meters up to ~15 km, and a set of four 12-m and twelve 7-m antennas operating in closely packed configurations ~50m
in diameter. The instrument will provide both interferometric and total-power astronomical information on high-energy
electrons, molecular gas and dust in solar system, our Galaxy, and the nearby and high-redshift universe. In this paper
we outline the scientific drivers, technical challenges and construction status of ALMA.