| Alexander Fairley Buchan | |
| Birth Place: | Edinburgh, Scotland |
| Death Place: | Edinburgh, Scotland |
| Alma Mater: | University of Edinburgh |
| Thesis Title: | Linear Combination of Data with Least Error of Differences |
| Thesis1 Url: | and |
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| Thesis Year: | 1939 |
| Doctoral Advisor: | Alexander Aitken |
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Alexander Fairley Buchan (1904 – 10 January 1976) was a Scottish mathematician. Most of his career was spent as a lecturer or teacher in mathematics. He completed his PhD in mathematics in 1939 with a thesis entitled, "Linear Combination of Data with Least Error of Differences". Buchan was awarded an MBE for his work as part of the emergency scheme for training of teachers in India. From 1940, he was a Fellow of the Royal Society of Edinburgh.
Buchan was born in Edinburgh, Scotland in 1904. He attended Sciennes School, Edinburg in 1916 then George Heriot's School from 1916 to 1922, where he obtained high level passes in English, Mathematics, German, Science, and Dynamics. He attended the University of Edinburgh from 1922 to 1926, and was awarded a BSc (first class).
Buchan went on to become a mathematics teacher at James Gillespie's High School, Edinburgh until 1930 when he joined the Royal High School, Edinburgh. In 1935 he moved to James Gillespie's High School for Girls as principal teacher of mathematics. His final posting was as principal lecturer in mathematics at Moray House College of Education. In 1941 he co-presented a lecture to the Edinburgh Mathematics Society entitled "Has mathematics as it is or could be taught in schools, any cultural or educational value for the average pupil?"