We have used the Hubble Space Telescope Faint Object Spectrograph to observe the mid-UV spectrum of the ROSETTA mission target comet, 46P/Wirtanen, on three dates during the comet's apparition in 1996 and early 1997. Dur- ing this time the comet moved inward from a heliocentric dis- tance near 2.7 AU to 1.3 AU. The first measurement (22.7 July 1996) detected only reflected solar continuum; based on these measurements, we set an upper limit on the nuclear radius of 1.45 km. A second measurement (25.9 Aug 1996) detected this reflected continuum, as well as weak OH (0-0) emission; the third measurement (15.2 Jan 1997) detected three OH bands at high signal-to-noise (the 0-0, the 1-0, and the 1-1), along with emission features from the CS radical and the CO + ion; up- per limits on their emission brightness and production rate of C2 was set. Our key findings are as follows: The data indicate that Q(H2O) varies like R 4:90:25 inside 2.5 AU, and that the CS2/H2O production ratio at 1.3 AU is close to310 4 . We also found that the 2600-3200 ˚ A mid-UV coma color slope is more neutral (25%/1000 ˚ A) than typical comets (40-70%/1000 ˚ A, but is steeper than Wirtanen's own visible-wavelength color slope. Wirtanen's CS 2/H2O production ratio is near the low end of the range observed to date. Af was estimated from the data as a measure of dust production; we found Af (2950 ˚ A) values of 15, 18, and 15 cm, respectively, for the three FOS datasets, after correction for the estimated flux contribution of the nu- cleus. Interestingly, we found that production of dust, to which the UV is sensitive, did not appear to vary by more than a factor of about two with heliocentric distance over the 2.7 to 1.3 AU range, despite a factor of 50 variation in the production of H2O.