Middelthun was born at
Kongsberg in
Buskerud, Norway. He was the son of Georg Middelthun (1779–1831) and Maren Margrethe Jørgensen (1785–1829). His father was employed at the
Royal Norwegian Mint in Kongsberg. As a young man, he trained as a
goldsmith before moving to
Copenhagen to study with
Herman Wilhelm Bissen. His ten years there were followed by eight years in
Rome (1851–1856), after which he returned to Norway. ==Selected works==