Sir Alexander Gillies (26 September 1891 – 19 February 1982) was a New Zealand orthopaedic surgeon who played a major role in establishing orthopaedics as a surgical speciality in New Zealand. One of the first to practise hip replacement in New Zealand, he was prominent in the foundation of the New Zealand Orthopaedic Association and became its first president. He was associated with a number of humanitarian causes including the New Zealand Red Cross Society of which he was chairman and latterly president.