  This is the first of three plenary talks with the same title given at the
28th ICRC in Tsukuba, Japan in August, 2003. A brief description of the
techniques for detecting gamma rays at TeV energies is followed by a summary of
the observational status of the field. The expectations of the field from a
cosmic ray perspective are compared with these early results. The majority of
sources detected with some certainty are extragalactic; the observational
status of these sources is summarized. The most complete set of observations
are those dealing with the detection of blazars for which a catalog is
presented. This discipline is now established as a new branch of observational
astronomy.
