John Webster Kirklin (April 5, 1917 – April 21, 2004) was an American cardiothoracic surgeon, general surgeon, prolific author and medical educator who is best remembered for refining John Gibbon's heart–lung bypass machine via a pump-oxygenator to make feasible under direct vision, routine open-heart surgery and repairs of some congenital heart defects. The success of these operations was combined with his other advances, including teamwork and developments in establishing the correct diagnosis before surgery and progress in computerized intensive care unit monitoring after open heart surgery.