Rufus Daniel Isaacs, 1st Marquess of Reading (10 October 1860 - 30 December 1935) was a British politician and jurist.

A prosperous lawyer, Isaacs entered the Commons as a Liberal in 1904, and went on to serve as Solicitor-General and Attorney-General in the governments of Sir Henry Campbell-Bannerman and Herbert Henry Asquith, becoming the first Attorney-General to sit in the Cabinet in 1912. In 1913, Isaacs was made Lord Chief Justice, a position in which he served until 1921. He was raised to the peerage as Lord Reading of Erleigh in 1914, and continued to rise to the peerage, being made a Viscount in 1916 and an Earl in 1917. In 1918, he was appointed Ambassador to the United States, a position in which he served until 1919, while continuing at the same time as Lord Chief Justice. In 1921, he resigned the chief justiceship to become Viceroy of India. Although Reading preferred a conciliatory policy, he ended up using force on several occasions, and imprisoned Mahatma Gandhi in 1922. On his return in 1926, he was advanced to a Marquess. In MacDonald's National Government in August 1931, he briefly served as Secretary of State for Foreign Affairs, but stood down after the first major reshuffle in November due to ill-health.

Reading rose higher in the peerage than any other Jew in British history.

|- style="text-align: center;" | width="30%" |Preceded by:
The Lord Chelmsford | width="40%" style="text-align: center;" |Viceroy of India
1921–1925 | width="30%" |Succeeded by:
The Earl of Lytton

|- style="text-align: center;" | width="30%" |Preceded by:
The Lord Parmoor | width="40%" style="text-align: center;" |Leader of the House of Lords
1931 | width="30%" |Succeeded by:
The Viscount Hailsham

|- style="text-align: center;" | width="30%" |Preceded by:
Arthur Henderson | width="40%" style="text-align: center;" |Foreign Secretary
1931 | width="30%" |Succeeded by:
Sir John Simon

|- style="text-align: center;" | width="30%" |Preceded by:
The Earl Beauchamp | width="40%" style="text-align: center;" |Lord Warden of the Cinque Ports
1934–1935 | width="30%" |Succeeded by:
The Marquess of Willingdon