John “Steve” Stevenson (born 1930) is a British writer who, under the pen name Marcus van Heller, wrote erotic fiction for the Traveller’s Companion series of Olympia Press publisher (1955–1961). Later he also wrote under the pen name Stephen John.
In 1954, at the age of 23, John Stevenson arrived for a sojourn in Paris, where he socialised with the expatriate community behind the modernist literary magazine Merlin. He soon became the business manager for Merlin. As the magazine was not well known to the public, the job consisted mostly of selling copies on the street.