Prof Duncan MacLaren Young Sommerville (1879–1934) was a Scottish mathematician and astronomer.
He compiled a bibliography on non-Euclidean geometry and also wrote a leading textbook in that field.
He also wrote Introduction to the Geometry of N Dimensions, advancing the study of polytopes.
He was a co-founder and the first secretary of the New Zealand Astronomical Society.
Sommerville was also an accomplished watercolourist, producing a series New Zealand landscapes.
The middle name 'MacLaren' is spelt using the old orthography M'Laren in some sources, for example the records of the Royal Society of Edinburgh.