Sir Charles Henry Knowles, 2nd Baronet, GCB (24 August 1754 – 28 November 1831) was an officer of the Royal Navy, who saw service during the American War of Independence, and the French Revolutionary and Napoleonic Wars, eventually rising to the rank of Admiral. He was an extraordinary figure and a great tactical innovator. Highly intellectual, he authored a number of signal books and had the chance to put his ideas into practice during his naval career. Knowles was at times beset by problems with discipline aboard his ships, often due to large proportions of raw recruits and untrained seamen. This may have been a factor in his rocky relationship with his superior, Sir John Jervis, which eventually led to Knowles's retirement from active service after the Battle of Cape St Vincent, and his concentration on scholarly studies of the issues affecting the naval service.