Prof **Andrew Russell Forsyth** FRS FRSE (18 June 1858, Glasgow – 2 June 1942, South Kensington) was a British mathematician.

Forsyth was born in Glasgow on 18 June 1858, the son of John Forsyth, a marine engineer, and his wife Christina Glen.

Forsyth studied at Liverpool College and was tutored by Richard Pendlebury before entering Trinity College, Cambridge, graduating senior wrangler in 1881. He was elected a fellow of Trinity and then appointed to the chair of mathematics at the University of Liverpool at the age of 24. He returned to Cambridge as a lecturer in 1884 and became Sadleirian Professor of Pure Mathematics in 1895.

Forsyth was forced to resign his chair in 1910 as a result of a scandal caused by his affair with Marion Amelia Boys, *née* Pollock, the wife of physicist C. V. Boys. Boys was granted a divorce on the grounds of Marion's adultery with Forsyth. Marion and Andrew Forsyth were later married.

Forsyth became professor at the Imperial College of Science in 1913 and retired in 1923, remaining mathematically active into his seventies. He was elected a Fellow of the Royal Society in 1886 and won its Royal Medal in 1897.

He is now remembered much more as an author of treatises than as an original researcher. His books have, however, often been criticized (for example by J. E. Littlewood, in his *A Mathematician's Miscellany*). E. T. Whittaker was his only official student.

He died in London on 2 June 1942 and was cremated at Golders Green Crematorium.

Forsyth married Marion Amelia Pollock in 1910.

A Treatise on Differential Equations (1885)
Theory of Functions of a Complex Variable (1893)
Geodesics on an oblate spheroid(1895–96)
Theory of Differential Equations (1890-1906) six volumes
Lectures on the Differential Geometry of Curves and Surfaces (1912)
Lectures Introductory to the Theory of Functions of Two Complex Variables(1914)
Calculus of Variations (1927)
Geometry of Four Dimensions (1930)
Intrinsic Geometry of Ideal Space (1935)