Ian Aird (4 July 1905 – 17 September 1962) was a Scottish surgeon who became Professor of Surgery at the Royal Postgraduate Medical School in London. There he built up a large and productive research department which made particular contributions in cardiac surgery, renal transplantation and the association of blood groups with stomach cancer. He came to national and international prominence in 1953 when he led the teams which performed an operation to separate conjoined twins. His book A Companion in Surgical Studies was among the best selling surgical textbooks of its day. He died suddenly in 1962 at the age of 57.