Any of 100 small, relatively isolated clusters of galaxies listed in a catalogue published in 1982 by the British-born Canadian astronomer Paul Hickson (1950– ). A typical Hickson compact group contains four to five closely spaced members, up to half of which may be interacting or even merging. Well-known examples of Hickson compact groups are Stephan’s Quintet (HCG 92) and Seyfert’s Sextet (HCG 79).