Katharine Macmillan, Viscountess Macmillan Of Ovenden

Katharine Margaret Alice Macmillan, Viscountess Macmillan of Ovenden (née Ormsby-Gore), was born on January 4, 1921. She was the daughter of the 4th Baron Harlech and the granddaughter of the 4th Marquess of Salisbury. Her maternal lineage also includes the 10th Marquess of Huntly.

On August 22, 1942, she married Maurice Macmillan, a Conservative politician. Through this marriage, she became the daughter-in-law of Harold Macmillan, who served as Prime Minister of the United Kingdom from 1957 to 1963. They had five children: Alexander Daniel Alan Macmillan, born in 1943, who became the 2nd Earl of Stockton; Joshua Edward Andrew Macmillan (1945–1965); Adam Julian Robert Macmillan (1948–2016); Rachel Mary Georgia Macmillan (1955–1987); and David Maurice Benjamin Macmillan, born in 1957.

Katharine Macmillan held the position of Vice-Chairman of the Conservative Party in 1968. She was appointed a Dame Commander of the Order of the British Empire (DBE) in 1974. In February 1984, she was granted the title Viscountess Macmillan of Ovenden, following her father-in-law Harold Macmillan's acceptance of a peerage as Earl of Stockton. Her husband, Maurice Macmillan, died in March 1984, the month after Harold Macmillan's elevation, and did not inherit the earldom.

Katharine Macmillan passed away on January 22, 2017.