We present Keck high-resolution near-IR (2.2 mu m; FWHM similar to 0."15) a
nd mid-IR (12.5 mu m; FWHM similar to 0."4) images of APM 08279 + 5255, a z
= 3.91 IR-luminous broad absorption line quasi-stellar object with a prodi
gious apparent bolometric luminosity of 5 x 10(15) L., the largest known in
the universe. The K-band image shows that this system consists of three co
mponents, all of which are likely to be the gravitationally lensed images o
f the same background object, and the 12.5 mu m image shows a morphology co
nsistent with such an image configuration. Our lens model suggests that the
magnification factor is similar to 100 from the rest-frame UV to mid-IR, w
here most of the luminosity is released. The intrinsic bolometric luminosit
y and IR luminosity of APM 08279 + 5255 are estimated to be 5 x 10(13) L. a
nd 1 x 10(13) L., respectively. This indicates that APM 08279 + 5255 is int
rinsically luminous, but it is not the most luminous object known. As for i
ts dust contents, little can be determined with the currently available dat
a because of the uncertainties associated with the dust emissivity and the
possible effect of differential magnification. We also suggest that the len
sing galaxy is likely to be a massive galaxy at z similar to 3.