We report the discovery of a new eclipsing millisecond binary pulsar system, PSR J2051-0827. The pulsar has a period of 4.5 ms and is in a very compact circular orbit with a companion of mass ∼0.03 M⊙. Observations at low frequencies show that the eclipse duration is approximately 10% of the orbital period. However, at high radio frequencies, pulses are often detected throughout the eclipse region, revealing interesting time-variable density structure in the eclipsing plasma. © 1996. The American Astronomical Society. All rights reserved.