Isaach Isaachsen (25 May 1774 – 15 August 1828) was a Norwegian politician.
He was born in 1774 as the son of wealthy businessman Daniel Isaachsen[1] and his first wife Christiane Hedvig Christensen. He married a Hedevig Elisabeth Hansen. He was the brother of Peder and Daniel Otto Isaachsen.[1]
His son Daniel became a jurist. Through him, Isaach Isaachsen was the grandfather of painter Olaf Isaachsen.[1]
He was elected to the Norwegian Parliament in 1818, representing the constituency of Lister og Mandals Amt. He worked as a farmer there. He served only one term.[2]