Jacob Thurmann Ihlen (17 May 1833 – 10 October 1903) was a Norwegian barrister and politician for the Conservative Party.
He was born in Holmestrand as the son of ship-owner Nils Ihlen (1793–1865) and Barbara Wincentz Thurmann (1800–1879).
[2] He married Belgian citizen Ambroisine Pauline Rouquet in February 1868 in Our Saviour's Church,[3] and the couple had five children.
[6] Their son Jacob Ihlen was an attorney and captain, and owned the property Parkveien 37 for some time.
[8][9] He was elected to the Parliament of Norway in 1883, and re-elected in 1886, representing the urban constituency of Kristiania, Hønefoss og Kongsvinger.