  We report the imaging and spectroscopic localization of GRB 060218 to a
low-metallicity dwarf starburst galaxy at z = 0.03345 +/- 0.00006. In addition
to making it the second nearest gamma-ray burst known, optical spectroscopy
reveals the earliest detection of weak, supernova-like Si II near 5720
Angstroms (0.1c), starting 1.95 days after the burst trigger. UBVRI photometry
obtained between 1 and 26 days post-burst confirms the early rise of supernova
light, and suggests a short time delay between the gamma-ray burst and the
onset of SN 2006aj if the early appearance of a soft component in the X-ray
spectrum is understood as a ``shock breakout''. Together, these results verify
the long-hypothesized origin of soft gamma-ray bursts in the deaths of massive
stars.
