[1] He was born in Bergen, Norway as a son of police chief and burgomaster Albert Lassen (1783–1860) and his wife Abigael Vogt Monrad (1792–1861).
He attended Bergen Cathedral School and graduated from the University of Christiania in 1843.
Lassen portrayed Wergeland as a wordsmith first and foremost, not as a liberal political figure.
[4] Lassen died during 1897 in Christiania and was buried at Vår Frelsers gravlund.
In 1915, the Hartvig Lassens medalje was established at the University of Oslo for outstanding literary dissertations.