We present the first rest-frame \sim 4 \mu m detection of a Lyman break galaxy .
The data were obtained using the 16 \mu m imaging capability of the Spitzer Infrared Spectrograph .
The target object , J134026.44+634433.2 , is an extremely luminous Lyman break galaxy at z=2.79 first identified in Sloan Digital Sky Survey spectra ( Bentz , Osmer , & Weinberg 2004 ) .
The source is strongly detected with a flux of 0.94 \pm 0.02 mJy .
Combining Spitzer and SDSS photometry with supporting ground-based J- and K-band data , we show that the spectral energy distribution is consistent with an actively star-forming galaxy .
We also detect other objects in the Spitzer field of view , including a very red MIR source .
We find no evidence of a strong lens amongst the MIR sources .