Margaret McMillan CH CBE (July 1860 – 27 March 1931) was a nursery school pioneer and lobbied for the 1906 Provision of School Meals Act. Working in deprived districts of London, notably Deptford, and Bradford, she agitated for reforms to improve the health of young children, wrote several books on nursery education and pioneered a play-centred approach that has only latterly found wide acceptance.
Margaret McMillan, was born to James and Jean McMillan in Westchester County, New York, on 20 July 1860. Her parents, were from Inverness but had emigrated to the United States in 1840. When she was four, an epidemic of Scarlet fever killed her father and sister and left Margaret deaf (she recovered her hearing at the age of fourteen). Thereupon Mrs. McMillan returned to Scotland with her daughters Margaret and Rachel McMillan, where both attended the Inverness High School. McMillan's mother Jean McMillan died in 1877.
McMillan went on to study Psychology and Physiology, followed by Languages and Music in Germany. In 1887 McMillan was introduced to Christian socialism and read articles by William Morris and William Thomas Stead and after July 1888 joined her sister in London. Together they attended political meetings, where they met Morris, H. M. Hyndman, Peter Kropotkin, William Stead and Ben Tillett. In 1889, McMillan and her sister helped the workers during the London Dock Strike. In 1892 they moved to Bradford. There they joined the Fabian Society, the Labour Church, the Social Democratic Federation and the Independent Labour Party (ILP).
With Bradford's school medical officer, Dr. James Kerr, McMillan carried out the first medical inspection of elementary school children in Britain. They published a report and began a campaign for local authorities to install bathrooms, improve ventilation and supply free school meals for children, after seeing the success of Bradford Cinderella Club providing a warm meal to underprivileged children.
In 1902 the sisters joined the recently formed Labour Party, working with James Keir Hardie and George Lansbury. McMillan began to write books on health and education. In 1904 she published her most important books, Education Through the Imagination and The Economic Aspects of Child Labour and Education. Through McMillan's work and joint campaigning with Katharine Glasier, the House of Commons passed the 1906 Provision of School Meals Act.
In 1908 McMillan and her sister opened England's first school clinic at Bow followed by the Deptford Clinic in 1910. A Night Camp where slum children could wash and wear clean nightclothes followed. In The Child and the State published in 1911, McMillan argued that schools should be offering a broad and humane education instead of preparing children for unskilled, monotonous jobs.
McMillan and her sister campaigned for Universal suffrage. McMillan was injured while protesting the way Women's Social and Political Union members were treated in prison through the Cat and Mouse Act.
In 1914 the sisters founded the Open-Air Nursery School & Training Centre in Deptford for children from eighteen months to seven years and for adult trainees. McMillan invited personalities like Bernard Shaw and Walter de la Mare to speak to audiences in Deptford. On 25 March 1917 her sister Rachel McMillan died. McMillan continued to run the Nursery, which she named the Rachel McMillan College after her sister. Margaret McMillan's nursery in Deptford was the first to receive local education authorities (LEAs) funding in 1917.
In 1922 she was brought in touch with the work of Rudolf Steiner through Prof Millicent Mackenzie and joined the initiative Educational Union for the Realization of Spiritual Values in Education, becoming one of the organisers and presiding over the 1923 conference in Ilkley where Steiner held the lecture cycle The New Art of Education. Steiner acknowledged the work McMillan was doing, referring to her as an educational genius in his subsequent report. McMillan visited Dornach in Switzerland and saw the first Waldorf school. She remained connected with the work of Anthroposophy and assisted the growing Steiner school's movement. Later in life she became interested in the subject of nursing and established the Rachel McMillan College to train nurses and teachers in Deptford in May 1930.
McMillan died in Harrow, London in 1931.
The Rachel McMillan College, named after Margaret's sister, was founded in 1930 and merged with Goldsmiths College in the 1970s, although student accommodation still exists in Creek Road, Deptford, bearing her name.
In early May 1936 the Duke of York opened Margaret McMillan House. The first purpose-built outdoor centre created in memory of Margaret McMillan. The centre is now part of the charity, Widehorizons, which delivers a range of adventure based activities.
A memorial college to Margaret McMillan was opened in Bradford in 1952.
An award-winning park named after her  stands on the site of what was once one of the most deprived streets in Deptford, as shown on the Poverty map published by Charles Booth (social reformer) 
The Life of Rachel McMillan by Margaret McMillan. J.M. Dent and Sons, London (1927)
Child Labour and the Half-time System (Clarion pamphlet) by Margaret McMillan (1896) "Clarion" Newspaper Co (1896) ASIN B0008BN3JG
The Passing of Rudolf Steiner McMillan, Margaret. 1925 Article: Journal of Education and School World 57 (June): 392-393.
- Margaret McMillan, Spartacus Education, retrieved 13 August 2011
- McMillan Margaret, Biographische Dokumentation der Forschungsstelle Kulturimpuls, retrieved 8 September 2014
- Pam Hirsch; Mary Hilton (30 July 2014). Practical Visionaries: Women, Education and Social Progress, 1790-1930. Routledge. p. 197. ISBN 978-1-317-87722-6.
- Rudolf Steiner in Britain by Crispian Villeneuve. Temple Lodge Press 2009 ISBN 978-1-906999-03-2
- Miriam Lord, History to Her Story, archived from the original on 29 September 2011, retrieved 13 August 2011
- "McMILLAN, Margaret (1860-1931) & McMILLAN, Rachel (1859-1917)". English Heritage. Retrieved 24 August 2014.
- "London Gardens Online, Margaret McMillan Park". Retrieved 26 October 2018.
- "Charles Booth's London Poverty Maps and Police Notebooks". Retrieved 26 October 2018.
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| Southern Division representative on the Independent Labour Party National Administrative Council