| Election Name: | 1945 Combined Scottish Universities by-election |
| Type: | parliamentary |
| Country: | United Kingdom |
| Seats For Election: | Constituency of Combined Scottish Universities |
| Ongoing: | no |
| Previous Election: | 1938 United Kingdom general election |
| Previous Year: | 1938 |
| Election Date: | 9–13 April 1945 |
| Candidate1: | John Boyd Orr |
| Party1: | Independent (politician) |
| Popular Vote1: | 20,197 |
| Percentage1: | 71.2% |
| Candidate2: | R. M. Munro |
| Party2: | National Liberal Party (UK, 1931) |
| Popular Vote2: | 8,177 |
| Percentage2: | 28.8% |
| MP | |
| Posttitle: | Subsequent MP |
| Before Election: | George Morrison |
| Before Party: | National Liberal Party (UK, 1931) |
| After Election: | John Boyd Orr |
| After Party: | Independent (politician) |
| Turnout: | 44.6% (7.5%) |
| Next Election: | 1945 United Kingdom general election |
| Next Year: | July 1945 |
The 1945 Combined Scottish Universities by-election was a by-election held from 9 to 13 April 1945 for the Combined Scottish Universities, a university constituency of the British House of Commons.
The seat had become vacant on 6 March 1945 when the National Liberal Member of Parliament (MP) George Morrison had resigned by the procedural device of accepting the post of Crown Steward and Bailiff of the Manor of Northstead, a notional 'office of profit under the crown' which is used as a procedural device to enable MPs to resign from the Commons.
Two candidates contested the by-election. The Rector of the University of Glasgow, Sir John Boyd Orr, stood as an independent. He was a doctor and biologist, and founder of the Rowett Research Institute.
The other candidate was R. M. Munro of the National Liberal Party.
The result was a victory for Boyd Orr, who won over 70% of the votes. He held the seat until 1946, when he resigned to take up the post of Director of the United Nations Food and Agriculture Organization.