Craigie Mason Aitchison KC (26 January 1882 – 2 May 1941) was a Scottish politician and judge.
Mason was born in Falkirk, where his father Reverend James Aitchison was the senior minister of the Erskine United Free Church.
Educated at Falkirk High School and at Edinburgh University, where he was the Vans Dunlop Scholar in Mental Philosophy and Muirhead Prizeman in Civil Law. He graduated from Edinburgh with an MA in 1903 and an LLB in 1907.
Aitchinson became an advocate in 1907. He was particularly effective as a defence counsel in criminal cases, and was regarded as the best advocate before a jury since Sheriff Comrie Thomson. He was noted for the Bickerstaff and John Donald Merritt cases.
He was made a King's Counsel in 1923. He worked with Sir Arthur Conan Doyle and others to secure the release of Oscar Slater, the victim one of the most notorious miscarriages of justice of the early twentieth century. Aitchison who was leading Counsel at the appeal in 1929 gave a 14-hour speech.
An unsuccessful Liberal candidate for Clackmannan and East Stirlingshire in November 1922 and December 1923, he joined the Labour Party and contested The Hartlepools at the October 1924 general election and Glasgow Central in May 1929 — where he reduced a Unionist majority of nearly 6,000 to only 627.