  The bulge contains the most chemically evolved old stellar population in the
Milky Way. Thanks to microlensing, it is now possible to obtain high resolution
echelle spectra of bulge stars near the main sequence turn-off, and study the
abundance of elements that are affected by stellar evolution, such as lithium.
We have observed with the HIRES spectrograph on the Keck I 10m telescope the
source star of the MACHO microlensing event 97BLG45 while it was magnified by
about 1 magnitude. Here we report the detection of the Li I line at \lambda
6707.8 \AA in the echelle spectrum of this star, and measure the bulge lithium
abundance for the first time: A(Li) = 2.25 \pm 0.25.
