Institut de recherche sur les lois fondamentales de l'Univers

The gamma-ray sky at very high energies (VHE, > 1e11 eV) is far from barren. Observations by new facilities in the past years have revealed new, unsuspected sources with a rich phenomenology. Binaries are amongst these sources. Their VHE lightcurves are modulated on their orbital period. I will review the observations and physical processes at work in these intriguing systems. The gamma-ray binaries are likely to harbour very young neutron stars and I will discuss what the systems might teach us about the physics of relativistic pulsar winds, one of the long standing problems of high energy astrophysics.