This paper describes the firsst light and subsequent test observations with the 8.2 m aperture Subaru Telescope constructed at the summit of Mauna Kea. Following the engineering first light, which started 1998 December, the astronomical first light and test observations were carried out in 1999 January with 4 testing instruments under seeing conditions of 0."2-0."5 for near-infrared and 0."3-0."6 for optical wavelengths. The actively supported primary mirror was shown to achieve an overall imaging performance of 0."1 (FWHM) or better in the absence of any atmospheric disturbance. The pointing accuracy of the telescope is about 1" rms, and a closed-loop tracking accuracy of less than or similar to 0."07 rms has been achieved. Infrared images of the Orion Nebula covering 5' x 5', obtained with J, K', and H-2 v = 1-0S(1) filters, have revealed much finer and fainter details of the BN/KL region, the bright bar, and other conspicuous features compared with previous observations. K' band photometry of 516 point sources yielded a luminosity funcion with a peak at K' similar to 12 mag with a long tail in K' similar to 13 mag down to K' similar to 17 mag, suggesting a fairly large number of young brown dwarfs existing in the Trapezium cluster. Several new features around the Orion BN/KL region are also reported.