Karenus Kristofer Thinn (19 December 1850 – 24 March 1942) was a Norwegian judge.
He was born in Østre Toten. From 1891 he was a presiding judge (lagmann) in Hålogaland, Borgarting and Agder. In 1902 he was appointed extraordinary Supreme Court assessor. From 1909 to 1920 he served as its tenth Chief Justice.