Campbell Duncan Mackellar was born on March 3, 1859, in Hamilton, Victoria, Australia.

He was an Anglo-Australian author who also wrote under the pseudonyms of “H.R.H.” and “Hilarion.” Little is known of his early life. After leaving Australia, he became a European celebrity, thanks to his interest in Balkan politics. MacKellar wrote novels, short stories, and dramatic sketches. All were published in Britain, except the short story collection “The Premier's Secret and Other Tales” (1887), published in Australia. He wrote “The Old Stradivari and Other Dramatic Sketches” (1894) and the novels “Lothair's Children” (1892), “A Jersey Witch” (1892), and “In Oban Town” (1896.) The other short story collection is “Grafin Rinsky and Other Tales” (1892). In 1890, he sent a letter to the editor of The Times, "The Proposed Antarctic Expedition." He published a travel book, "Scented Isles and Coral Gardens: Torres Straits, German New Guinea and the Dutch East Indies" (1912). He was a member of the Royal Geographical Society of Australia. MacKellar sponsored the Nimrod Expedition (1907-1909) led by British polar explorer Sir Ernest Shackleton and the Australasian Antarctic Expedition (1911-1914) led by Australian polar explorer Sir Douglas Mawson. Near the South Pole, there is a Mount Mackellar, named after him by Sir Ernest Shackleton, and, in the Antarctic, there is a group of islands, the Mackellar Isles, named after him by Sir Douglas Mawson.

He died on May 5, 1925, in London, England.