RMMV Capetown Castle was a British passenger liner built by Harland & Wolff at Belfast for the Union-Castle Line's mail service from Southampton to South Africa. She was launched in September 1937 and sailed on her maiden voyage on 29 April 1938.

The Union-Castle Line was a British shipping line that operated a fleet of passenger liners and cargo ships between Europe and Africa from 1900 to 1977. It was formed from the merger of the Union Line and Castle Shipping Line.