| Honorific-Prefix: | The Right Honourable |
| The Baroness Tweedsmuir of Belhelvie | |
| Office1: | Minister of State for Foreign and Commonwealth Affairs |
| Primeminister1: | Edward Heath |
| Term Start1: | 7 April 1972 |
| Term End1: | 4 March 1974 |
| Office2: | Minister of State for Scotland |
| Primeminister2: | Edward Heath |
| Term Start2: | 23 June 1970 |
| Term End2: | 7 April 1972 |
| Office3: | Parliamentary Under-Secretary of State for Scotland |
| Primeminister3: | Harold Macmillan Alec Douglas-Home |
| Term Start3: | 3 December 1962 |
| Term End3: | 16 October 1964 |
| Office5: | Member of Parliament for Aberdeen South |
| Term Start5: | 26 November 1946 |
| Term End5: | 10 March 1966 |
| Predecessor5: | Sir Douglas Thomson, Bt |
| Successor5: | Donald Dewar |
| Office4: | Member of the House of Lords Lord Temporal |
| Term Start4: | 1 July 1970 |
| Term End4: | 11 March 1978 Life peerage |
| Birth Name: | Priscilla Thomson |
| Birth Date: | 25 January 1915 |
| Death Place: | Aberdeenshire, Scotland |
| Party: | Scottish Conservative Party |
| Otherparty: | Unionist Party (until 1965) |
| Spouse: | |
Priscilla Jean Fortescue Buchan, Baroness Tweedsmuir of Belhelvie (née Thomson; 25 January 1915 – 11 March 1978), styled as Priscilla, Lady Grant between 1934 and 1944, and as Lady Tweedsmuir between 1948 and 1970, was a Unionist and Conservative politician.
The daughter of Brigadier Alan F. Thomson DSO, she married Major Sir Arthur Lindsay Grant, 11th Baronet, Grenadier Guards, in 1934. He was killed in action in 1944. She subsequently married author and politician the 2nd Baron Tweedsmuir in 1948.
Lady Tweedsmuir was an unsuccessful parliamentary candidate for Aberdeen North in July 1945, and was elected for Aberdeen South in 1946, holding the seat until 1966. She consistently polled at least 50% of the vote with the exception of her defeat in 1966, a feat never achieved by any succeeding candidates in the constituency.
She was a delegate to the Council of Europe from 1950 to 1953, a UK Delegate to the General Assembly of the United Nations, 1960–1961; Joint Parliamentary Under-Secretary of State for Scotland from 1962 to 1964.
On 1 July 1970 she was created a life peer as Baroness Tweedsmuir of Belhelvie, of Potterton in the County of Aberdeen.
Tweedsmuir was Minister of State at the Scottish Office from 1970 to 1972 and at the Foreign and Commonwealth Office from 1972 to 1974 and was sworn of the Privy Council in 1974. In the House of Lords she served as Principal Deputy Chairman of Committees, 1974–1977, and as Chairman of the Select Committee on European Communities, 1974–1977. She was also a Deputy Speaker.
She died of cancer in 1978, aged 63.
She was mentioned several times in the 2014 Loyal Address to Parliament on 4 June in the House of Commons by Penny Mordaunt.
In 1983, the veteran Labour politician Emanuel Shinwell stated Tweedsmuir was 'the best' female MP Britain had had.[1]