Plasma and magnetic field observations from the Voyager 2 spacecraft when it was outbound from Neptune reveal low-frequency waves in the solar wind which are clearly associated with the planet. The waves have frequencies below the proton cyclotron frequency fcp, which is about 10-3 Hz during the periods waves are observed. The waves are present when the interplanetary magnetic field is oriented such that the spacecraft is connected to the bow shock by the magnetic field lines. We have identified the waves to be Alfv¿nic waves propagating at ~140¿ to the ambient magnetic field and away from the bow shock. As at the other planets, these downstream waves are thought to be generated in the upstream region, where energetic protons created near the nose of the bow shock excite waves as they stream along solar wind magnetic field lines. ¿American Geophysical Union 1991