William Hardy Hendren (always known as Hardy) was universally accepted as being the leading American paediatric surgeon of his generation. Known worldwide for his meticulous surgical technique and his pioneering ability to correct seemingly intractable anatomical conditions, he was driven by the mantra that his operations had to last his young patients a lifetime. Hardy was equally well known for his astonishing stamina, sometimes operating on a single patient for 18 hours or more and his demand for surgical perfection. If necessary, he would undo many hours of work in order to redo an operation from the beginning. This work ethic led to his acquiring the nickname ‘Hardly Human’, a mark of affection by his devoted trainees and friends and a soubriquet of which he was secretly proud. Hardy was born on 7 February 1926 in New Orleans to a film industry executive, William Hardy Hendren Jr, and his wife, Margaret Inglis Hendren née McLeod, but spent much of his childhood in Kansas City. Later he attended Woodberry Forest School in Orange, Virginia, leaving at the age of 17 to enlist as an aviation cadet as part of the war effort. While waiting for his military call up, he studied at Dartmouth College for a semester. He earned his wings as a naval pilot but did not see combat service. On demobilisation in 1946 he re-enrolled at Dartmouth, gaining a bachelors degree in 1948 and then completed a two-year medical programme before transferring to Harvard, where he qualified MD *cum laude* in 1952. His paediatric training was at the Massachusetts General Hospital (MGH) and the Boston Children’s Hospital, where he was particularly influenced by Robert Gross. After eight years of paediatric training, he was appointed to MGH in 1960 to found the department of pediatric surgery, where he served as chief for 22 years. During this time, he became recognised for developing ground-breaking operations for complex genitourinary defects, which had previously been thought impossible to correct. In 1969 he became the first surgeon in Boston to successfully separate conjoined twins. International fame quickly developed, and he was invited to lecture, teach and operate in more than 60 countries worldwide. He was a prolific publisher of more than 200 scientific articles, 100 book chapters and six books, as well as making medical educational films. Honours included the William E Ladd Medal of the American Academy of Pediatrics, the Ferdinand C Valentine Medal of the New York Academy of Medicine, the Denis Browne Medal of the British Association of Paediatric Surgeons, the Urology Medal of the urologic section of the American Academy of Pediatrics, the Henry Jacob Bigelow Medal of the Boston Surgical Society, the Distinguished Service Award of the American Pediatric Surgical Association and the Jacobson Innovation Award from the American College of Surgeons. Hardy became an officer in many professional organisations, twice being elected president of the American Pediatric Surgical Association. He served as vice president of the American College of Surgeons and, in 2000, was awarded the honorary fellowship of the Royal College of Surgeons of England. In 2008, the Hendren Chair in Surgery was established at the Harvard Medical School. Two endowed fellowships were established in his name and a third was given to the Boston Children’s Hospital by grateful families whose children he helped surgically. The Hendren Project was established in 2014, an online global community of paediatric surgeons and urologists to provide digital resources that enable members to connect, collaborate and discuss difficult patient problems. This has grown to comprise over 5,000 members in over 140 countries, ensuring that Hardy’s name will live on. His biography, by G Wayne Miller, *The work of human hands: Hardy Hendren and surgical wonder at Children’s Hospital* was published in 1993 (New York, Random House). Despite his fame and extensive CV, Hardy remained a self-effacing humble man, a friend to all, most especially his patients as he followed their lives into adulthood. He and his wife of 75 years, Eleanor (née McKenna), whom he married in 1947, had five children. They were wonderful hosts to visiting surgeons the world over as the writer can testify, having been entertained by them on his first visit to Boston and later becoming a personal friend. Hardy’s interests outside of surgery included motor cycling, skiing, water-skiing and woodworking. He died peacefully at the age of 96 on 1 March 2022.