Carl Albert Hansen Fahlberg (January 14, 1870 – July 30, 1939) was a Danish author and police officer. Born out of wedlock to Søren Christian Ravnholdt (1826–1895) and Ellen Henriette Jacobine Hansen (1831-1888), Carl Hansen was raised in poor circumstances by his long-widowed mother (her husband was First Lieutenant Hendrik Fahlberg, 1807-1867) as an ‘adopted’ child. After his apprenticeship as a brazier, he travelled for four years as a journeyman through Germany, Austria, Italy, France and Switzerland. For more than a year he lived in Berlin and was introduced to its large homosexual subculture through a love affair with a male prostitute. In 1895, after doing military service, he became a constable in the Copenhagen Police Department. Under the pen name of ‘Albert Hansen’ he published an article in Magnus Hirschfeld's journal, Jahrbuch für sexuelle Zwischenstufen (1901), in which he undertook to prove that the fairy-tale author Hans Christian Andersen had been a homosexual. His novel Spild (Waste, 1905) was widely acclaimed for its realistic and compassionate descriptions of the harsh living conditions in the proletarian districts of Copenhagen. In 1897– 1903 he lived together with Hjalmar Sørensen. As a police officer Hansen was responsible for the introduction of the finger-printing method. In 1906 he was appointed police inspector and deputy commander of the Copenhagen CID. The same year he was implicated in a large homosexual scandal. After having been in custody for ten months, he suffered a nervous breakdown and was transferred to the psychiatric ward. Immediately after being released he mounted a ferocious attack on the judge in a series of newspaper articles. As a result, the key witness against him changed his testimony and thereby saved Hansen from being convicted for sodomy but not from being sentenced to two months of prison for gross indecency with minors.

In 1907 Hansen emigrated to the US, where he lived in Arkansas as a farmer until he was ruined in the Depression of 1929. He returned to Denmark in 1934. At a police parade the chief of police introduced him to younger colleagues as an early pioneer of criminal investigation and he received a small pension. In two autobiographical novels (published in 1937 and 1939), Hansen told the tale of his own childhood, of his years as a travelling journeyman, and of his time in Berlin – the first coming-out novels in Danish literature. He planned to write a third novel on his career as a police officer, which he had come to see as a kind of treason against his own class. In 1939 he took his own life.