Oz was first published as a satirical humour magazine between 1963 and 1969 in Sydney, Australia and, in its second and better known incarnation, became a "psychedelic hippy" magazine from 1967 to 1973 in London. Strongly identified as part of the underground press, it was the subject of two celebrated obscenity trials, one in Australia in 1964 and the other in the United Kingdom in 1971. On both occasions the magazine's editors were acquitted on appeal after initially being found guilty and sentenced to harsh jail terms.

The central editor throughout the magazine's life was Richard Neville. Co-editors of the Sydney version were Richard Walsh and Martin Sharp. Co-editors of the London version were Jim Anderson and, later, Felix Dennis.

Oz was parodied in the short-lived 1999 UK television series Hippies. Hippie Hippie Shake, a film based on Neville's memoir with Cillian Murphy in the lead role, will be released in 2011.^{[dated info]}

The original Australian editorial team included university students Neville, Walsh and Sharp and Daily Mirror cadet journalist Peter Grose. Other early contributors included future Time magazine critic and art historian Robert Hughes, student and future author Bob Ellis. Neville, Walsh and Sharp had each been involved in student papers at their respective Sydney tertiary campuses—Neville had edited the UNSW student magazine Tharunka, Walsh edited its University of Sydney counterpart Honi Soit and Sharp had contributed to the short-lived student magazine The Arty Wild Oat while studying at the National Art School in East Sydney. Influenced by the satirical style of Britain's New Statesman and Private Eye and the radical comedy of Lenny Bruce, Neville and friends decided to found a "magazine of dissent".