An eclipsing binary millisecond pulsar has been discovered in the globular cluster Terzan 5. This, the second known eclipsing binary pulsar after PSR1957 + 20, has a pulse period of 11.56 ms and a very short orbital period of 1.8 hr. In contrast to PSR1957 + 20, the eclipse duration is very variable and never less than one third of the orbital period. The pulsar is in a circular orbit of radius 0.11 light seconds, which implies a minimum companion mass of 0.089 solar, about four times the companion mass of PSR1957 + 20. Timing observations suggest an identification of the pulsar with a variable continuum source located about 30 arcsec west of the cluster center. The eclipse is due to absorption or scattering in a tenuous wind flowing from the companion star.