Alf Collett (8 August 1844-12 June 1919) was a Norwegian writer and historian.Alf Collett was born at Eidsvoll in Akershus, Norway.
He attended Oslo Cathedral School.
He was the second son of professor Peter Jonas Collett (1813-1851) and Camilla Collett (1813-1895).
His maternal uncles included Oscar and Henrik Wergeland, and his paternal uncles included Peter Severin Steenstrup.
He had one older brother Robert, a notable zoologist, and two younger brothers.
He married Mathilda Sophie Kallevig (1845-1915), but they did not have any children.He published many historical and genealogical works, the most important being En gammel Christiania-slægt.
Optegnelser om familien Collett og Christianias fortid (1883) and Gamle Christiania-Billeder (1893).