NGC 3603 is the most massive and luminous visible starburst region in the Galaxy. We present the first Chandra ACIS-I X-ray image and spectra of this dense, exotic object, accompanied by a deep centimeter-wavelength Australia Telescope Compact Array radio image at similar 1'' spatial resolution and Hubble Space Telescope/ground-based optical data. At the S/N 3 level, Chandra detects several hundred X-ray point sources (compared to the three distinct sources seen by ROSAT). At least 40 of these sources are definitely associated with optically identified cluster O- and W-R-type members, but most are not. A diffuse X-ray component is also seen out to ~2' (4 pc) from the center, probably arising mainly from the large number of merging/colliding hot stellar winds and/or numerous faint cluster sources. The point-source X-ray fluxes generally increase with increasing bolometric brightnesses of the member O/W-R stars, but with very large scatter. Some exceptionally bright stellar X-ray sources may be colliding wind binaries. The radio image shows (1) two resolved sources, one definitely nonthermal, in the cluster core near where the X-ray/optically brightest stars with the strongest stellar winds are located, (2) emission from all three known proplyd-like objects (with thermal and nonthermal components), and (3) many thermal sources in the peripheral regions of triggered star formation. Overall, NGC 3603 appears to be a somewhat younger and hotter scaled-down version of typical starbursts found in other galaxies.
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