Eke, Vincent RBaugh, Carlton MCole, ShaunFrenk, Carlos SNorberg, PederPeacock, John ABaldry, Ivan KBland-Hawthorn, JossBridges, Terry CCannon, RussellColless, MatthewCollins, ChrisCouch, WarrickDalton, GavinDe Propris, RobertoDriver, SimonEfstathiou, GeorgeEllis, Richard SGlazebrook, KarlJackson, CaroleLahav, OferLewis, IanLumsden, StuartMaddox, Steve JMadgwick, DarrenPeterson, BruceSutherland, William JTaylor, Keith2015-12-132015-12-130035-8711http://hdl.handle.net/1885/89465The construction of a catalogue of galaxy groups from the Two-degree Field Galaxy Red-shift 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 per cent of interlopers. About 55 per cent of the ∼190 000 galaxies considered are placed into groups containing at least two members of which ∼29 000 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 260 km s -1. This 2dFGRS Percolation-Inferred Galaxy Group (2PIGG) catalogue represents the largest available homogeneous sample of galaxy groups. It is publicly available on the World Wide Web.Keywords: Catalogues; Galaxies: Clusters: General20042015-12-12