Catherine Everit "Kate" Macy Ladd (1863–1945) was an American philanthropist who founded and endowed the Josiah Macy, Jr. Foundation in honor of her father.
Ladd was a descendant of Thomas and Sarah Macy, Massachusetts settlers in the late 1630s, and a granddaughter of Captain Josiah Macy, originally of Nantucket, who founded a firm that became New York's first oil refinery in the 1860s (later sold to the Standard Oil Company).
Ladd married lawyer and yachtsman Walter Graeme Ladd (1857–1933) on December 5, 1883. Their Peapack-Gladstone, New Jersey estate, Natirar, became a nonprofit organization. On Walter Ladd's death, and in accordance with his will, Natirar was sold to King Hassan II of Morocco. On the king's death in 1999 it was inherited by his son, Mohammed VI. More recently, Natirar has been leased by billionaire industrialist Sir Richard Branson of the Virgin Group. It is set to be converted into a spa, restaurant, and hotel complex called The Virgin Spa at Natirar.