Dame Henrietta Barnett (1851 – 1936) was a notable English social reformer. Married to Samuel Augustus Barnett, she helped found the first university settlement , Toynbee Hall in east London in 1884.

Born Henrietta Octavia Rowland, she worked with Octavia Hill who was instrumental in introducing her to the curate of St Mary’s, Bryanston Square , London. She subsequently married Samuel Barnett in 1873 and later that year the Barnetts moved to the impoverished Whitechapel parish of St Jude’s intent on improving social conditions.

A strong believer in the power of education to effect social change, she helped establish the Children's Country Holiday Fund (1884) and annual loan exhibitions of fine art at the Whitechapel gallery. The current Whitechapel Art Gallery was built in 1897 at the behest of the Barnetts, in the Arts and Crafts style.

She was also strongly associated with the Hampstead area of north-west London, conceiving the idea of the model housing development of Hampstead Garden Suburb in 1904 (working with architects Raymond Unwin and Sir Edwin Lutyens) and helping protect part of Hampstead Heath from development by Eton College. She lived at Heath End House in Spaniards Road, Hampstead (today marked by a blue plaque) until her death in 1936, 12 years after becoming Dame.

Barnett also founded the Henrietta Barnett school in Barnet in 1911.