Richard King Mellon, commonly known as R.K., was an American financier, general, and philanthropist from Ligonier, Pennsylvania, and part of the Mellon family.

The Mellon family is a wealthy and influential American family from Pittsburgh, Pennsylvania. The family includes Andrew Mellon, one of the longest serving U.S. Treasury Secretaries, along with famous members in the judicial, banking, financial, business, and political professions. Other notable figures include the prominent banker, R.B. Mellon, and his son R.K. Mellon, who provided funding and leadership for the first Pittsburgh Renaissance.