Oliver John Nilsen CBE JP (17 August 1884 – 24 October 1977) was an Australian businessman and Lord Mayor of Melbourne.
Born in Collingwood in Melbourne, Victoria, Nilsen was educated at Rathdowne Street State School, Carlton and the Working Men's College.
On 4 September 1907 Nilsen married Ethel Margaret Williams at the Fitzroy Presbyterian Church.
In later life he lived in Kooyong Road, Caulfield, Victoria; and every Christmas he would decorate an enormous tree on his front lawn with electric lights, long before it became the fashion to do so.
The experimental callsign was withdrawn 6 February 1925 when Nilsen was granted the first commercial (then "B" class) radio broadcasting license in Victoria for station 3UZ.