Cardiology (from Greek καρδίᾱ, kardiā, "heart"; and -λογία, -logia) is a medical specialty dealing with disorders of the heart (specifically the human heart). The field includes medical diagnosis and treatment of congenital heart defects, coronary artery disease, heart failure, valvular heart disease and electrophysiology. Physicians who specialize in this field of medicine are called cardiologists. Physicians who specialize in cardiac surgery are called cardiac surgeons.

Cardiology is specialty of internal medicine. To be a cardiologist in the United States, a three year residency in internal medicine is followed by a three year residency in cardiology. It is possible to specialize further in a subspecialty. Recognized subspecialties in the United States by the ACGME are:

As the center focus of cardiology, the heart has numerous anatomical features (e.g., atria, ventricles, heart valves) and numerous physiological features (e.g., systole, heart sounds, afterload) that have been encyclopedically documented for many centuries.

Paul M. Ridker is a medical researcher and the Eugene Braunwald Professor of Medicine at Harvard University. He is also on staff at Brigham and Women's Hospital in Boston, Massachusetts. Dr. Ridker was included in TIME magazine's list of 100 most influential people of 2004. Previously, TIME and CNN named Dr. Ridker as one of "America’s Best in Science and Medicine". He is responsible for the clinical development of high sensitivity C Reactive Protein (hsCRP), a marker of inflammation, that is used to evaulate the risk of heart attack and stroke.