Yellow diamonds are diamonds which have taken on a yellow tone, either through natural interruptions in their formation process or chemical treatment. Natural yellow diamonds are extremely rare, and the color is usually caused by nitrogen impurities that appear while the diamond is being formed. More commonly, yellow diamonds are synthesized in the lab; lab-made diamonds are chemically indistinct from natural diamonds, and are widely used in ornamental jewelry and some manufacturing processes.

Usually, clear diamonds are in high demand. A flawless clear diamond which is cut in a flattering way can fetch a great deal of money once set in a piece of jewelry, while a discolored diamond is not considered valuable. If, however, the color is strong and intense, it becomes what is known as a fancy diamond: a naturally colored diamond. Fancy diamonds such as yellow diamonds are handled and graded differently than clear diamonds, and some of the most famous diamonds in the world, such as the Hope Diamond, are fancy diamonds.