A Parliamentary Under-Secretary of State is the lowest of three tiers of government minister in the government of the United Kingdom, junior to both a Minister of State and a Secretary of State. Having been an under-secretary in Macmillan's 1957–1963 Conservative government, the Duke of Devonshire noted "No one who hasn't been a Parliamentary Under Secretary of State has any conception of how unimportant a Parliamentary Under Secretary of State is".
The position should not be confused with a Permanent Under-Secretary of State—commonly referred to as a Permanent Secretary—who is the chief civil servant in a Government department.