Alfred Selwyn was born in Somerset, England in 1824, and had a strong Church of England upbringing. He was educated in Switzerland where he developed an enthusiasm for geology. At the age of 21 he joined the Geological Survey of Great Britain although not a university graduate. He began work under the direction of A.C. Ramsey in North Wales and was soon entrusted with the independent mapping of large areas containing key Silurian rocks.

The discovery of gold in Victoria in 1851 led Governor La Trobe to ask the Colonial Office in London for "a gentleman possessed of the requisite qualifications and acquaintance with geological science and phenomenon." Selwyn was awarded the post at an annual salary of £500 and arrived in early December 1852.
Almost immediately he commenced a series of wide-ranging reconnaissance trips during which he studied the geology of Victoria, with additional excursions into Tasmania and South Australia. Selwyn set up the Geological Survey proper in 1856 and trained a team. of geologists including Aplin, Ulrich, Wilkinson, Daintree, Taylor, Brown and Etheridge. They subsequently occupied senior positions in other State Geological Surveys and became renowned in the early annals of Australian geology. Selwyn and his team established the Victorian quarter sheet mapping program, from which 65 maps were produced, each covering an area of six miles by nine miles.
Selwyn was a silent and reserved man of indomitable disposition who carried out his plans in spite of all hindrances and achieved an amount of work that few could emulate. However, conflict arose from the overlapping activities of mining surveyors. The Survey often held views on scientific standards and policies opposed to those of the colonial officials and legislators, in particular that of Robert Brough Smyth, Secretary of Mines. Consequently, Selwyn resigned in 1869 and the Survey was disbanded for a year.
Selwyn left Australia and was appointed the Director of the Geological Survey of Canada on the retirement of Sir William Logan. He filled this office with distinction from 1869 until his retirement in 1894. The Murchison Medal of the Geological Society of London was awarded to him in 1876. Other honours followed in Great Britain, but the only recognition from Australia was the Clarke Gold Medal from the Royal Society of New South Wales in 1884. He is commemorated in Victoria by the annual Selwyn Memorial Lecture, the highlight of the Selwyn Symposium. The Selwyn Medal is awarded annually to persons who have made significant contributions of high calibre to any field of Victorian geology.