Helen de Guerry Simpson (1 December 1897 – 14 October 1940) was an Australian novelist and British Liberal Party politician.

Simpson was born in Sydney into a family that had been settled in New South Wales for over 100 years. Her great-grandfather, Piers Simpson, R.N., was associated with Sir Thomas Mitchell and her maternal grandfather, the Marquis de Lauret, settled at Goulburn some 50 years before her birth. Her father, Edward Percy Simpson, was a well-known solicitor at Sydney who married Anne de Lauret. Helen Simpson was educated at the Rose Bay convent (now called Kincoppal-Rose Bay, School of the Sacred Heart) and at Abbotsleigh, Wahroonga and, in 1914, she went to France for further study. When war broke out she crossed to England and was employed by the admiralty in decoding messages in foreign languages. She then went to Oxford, studied music and, failing in her examination for the music bachelor's degree, took up writing.

She was an associate member of the Detection Club and contributed to two of their round-robin works The Floating Admiral (1931) and Ask a Policeman (1933) and the creative non-fiction The Anatomy of Murder (1936).

Boomerang, published in 1932, was her first big success. Its plot begins in Paris at the end of the eighteenth century, wanders all over the world, including Australia, and ends in the trenches in France during World War I. It was awarded the James Tait Black Memorial Prize for fiction and serialised for radio by William Power in 1937. -- Simpson was also the author of two pieces of historical biography, The Spanish Marriage (1933) and Henry VIII (1934). The Happy Housewife, a book of household management, was published in 1934. The Waiting City, which appeared in 1933, is her translation of a selection from Louis-Sébastien Mercier's Le Tableau de Paris. Three novels, Enter Sir John (1929), Printer's Devil (1930) and Re-enter Sir John (1932), were written in conjunction with Clemence Dane. Enter Sir John was filmed as Murder! (1930) directed by Alfred Hitchcock, who later directed the film version of Under Capricorn (1949). Helen Simpson also wrote portions of the dialogue for Hitchcock's movie Sabotage (1936).

In 1939 she was selected by the Isle of Wight Liberal Association to be their parliamentary candidate at the UK General Election which was expected to take place in 1939 or 1940. The seat was held by the Conservatives but the Liberals were expected to challenge strongly to recapture the seat they last won in 1923. She attended the Liberal Party Assembly at Scarborough in June 1939 and travelled around England speaking for the Liberal Party.

She became ill and underwent a surgical operation in 1940, but died from cancer after months of suffering on 14 October 1940. Her husband, Sir Denis Browne, survived her with a daughter. Her last novel, Maid No More, was published in 1940.