  The construction of a catalogue of galaxy groups from the 2-degree Field
Galaxy Redshift Survey (2dFGRS) is described. Groups are identified by means of
a friends-of-friends percolation algorithm which has been thoroughly tested on
mock versions of the 2dFGRS generated from cosmological N-body simulations. The
tests suggest that the algorithm groups all galaxies that it should be
grouping, with an additional 40% of interlopers. About 55% of the ~190000
galaxies considered are placed into groups containing at least two members of
which ~29000 are found. Of these, ~7000 contain at least four galaxies, and
these groups have a median redshift of 0.11 and a median velocity dispersion of
260km/s. This 2dFGRS Percolation-Inferred Galaxy Group (2PIGG) catalogue
represents the largest available homogeneous sample of galaxy groups. It is
publicly available on the WWW.
