Jacob Andreas Michelsen (17 August 1821 – 12 October 1902) was a Norwegian businessperson and politician, also known as the father of Christian Michelsen.

He was the son of Tollach Michelsen, a manual labourer with roots in the Egersund district. Tollach's wife Madsi Magdalena Eide (died 1829) came from the same social background.^[1]

In June 1855 he married Caroline Sophie Ernstine Kjerschow.^[1] Their son was the later Norwegian Prime Minister Christian Michelsen.^[2] Christian Michelsen was named after Jacob's father-in-law, bishop Peder Christian Hersleb Kjerschow.^[1]

Michelsen worked himself up from the modest social background. A businessman, he was awarded burghership in 1847. He was a grain trader,^[3] wine grocerer and consul,^[1] stock exchange commissioner from 1870 to 1902 and bank director from 1870.^[3] He served as mayor of Bergen from 1865 to 1866 and 1876 to 1878.^[4] He was elected from his city to the Norwegian Parliament in 1868 and 1871.^[5]

He died in 1902,^[1] three years before his son became Prime Minister.