The eminent naturalists, Richard Thomas Lowe, Thomas Vernon Wollaston and Hamlet Clark, have long been known to have undertaken expeditions on yachts owned by their rather obscure friend, a mysterious ‘Mr Gray’. Hitherto, very little was known of this man, now confirmed to be John Gray (1812–1881), a wealthy Lancashire cotton-mill owner. He owned three yachts at various times, and belonged to the Royal Mersey Yacht Club of Liverpool and the Royal Yacht Squadron of Cowes, Isle of Wight. A keen yachtsman, artist, and a member of the Entomological Society of London, he became an expert on beetles, of which he formed a scientifically important collection. Although Gray published nothing himself, he assisted in the fieldwork of Lowe and Wollaston in remote Macaronesian archipelagos, and Clark’s entomological expeditions in Spain and Algeria, by putting his yachts at their disposal and helping with beetle-collecting. He also accompanied Clark to Brazil, and Wollaston to St Helena, on passenger-steamers. During these expeditions, he collected spiders from the Cape Verde Islands and Brazil for the arachnologist, John Blackwall. At other times, travelling alone (either on his yacht or on steamships), he gathered insects from the West Indies, the USA and South Africa. Specimens collected by Gray and given to other entomologists, and remnants of his own collection auctioned off in 1883, are in the Bolton Museum, Lancashire; the Manchester Museum; the Hunterian Museum, Glasgow; and the Natural History Museum, London. At least one species of gastropod mollusc, fifteen species of beetles, and two species of spiders are named in Gray’s memory. He was also an enthusiastic water-colourist, but no examples of his paintings have been traced.