Marius Cathrinus Backer (25 June 1866 – 19 February 1960) was a Norwegian judge.
He was born in Drammen to timber trader Lars Zacharias Backer and Hanna Schwartz.
He graduated as cand.jur.
in 1888, and was named as a Supreme Court Justice from 1911 to 1936.
He was decorated Knight, First Class of the Order of St.