Lucy May Cranwell FRSNZ (7 August 1907 – 8 June 2000) was a New Zealand botanist responsible for groundbreaking work in palynology.

In April 1929, a few weeks after graduating, the director of the Auckland Museum, Dr Gilbert Edward Archey, offered Cranwell the inaugural Botany Curator position.

The museum was due to open in its new, much larger, war memorial building in November of that year and its halls were in need of filling with displays.

Dr Archey had stressed that we were to consider ourselves the servants of the public; we were to welcome enquiries of all kinds," wrote Cranwell of those first few months in the job.

During her 14 years as botany curator she introduced "botany trots" for children to places like Rangitoto Island in the Hauraki Gulf, wrote weekly short articles for children about plants for the Auckland Star newspaper, and collected over 4000 plants for the herbarium during her 14 years as the botanist.

Cranwell and her botanical companion Lucy Moore often slept out in the open in canvas sleeping bags, occasionally waking up covered in frost.

Her field experience led her to be a conservationist recognising early that possums and wallabies represented a serious threat to the biodiversity of New Zealand forests.

[1] During a trip to Europe, which included attending the International Botanical Congress in Amsterdam in 1935, she was invited by Professor Lennart von Post of Stockholm to learn his method of fossil pollen analysis.

Cranwell also recommended to the Ministry of Works that wattle trees, pampas grass and nasturtiums should be planted across New Zealand as emergency rations and stock feed.

[8] On 30 September 1943, Cranwell married Captain (later Major) Samuel Watson Smith (1897–1993) of the United States 13th Air Force, a lawyer and later eminent researcher in archaeology, at St Andrew's First Presbyterian Church.

[4] The family moved to Cambridge, Massachusetts in 1944,[4] where Smith worked at the Peabody Museum of Archaeology and Ethnology and Cranwell as a Research Associate in the Botany Department of Harvard University.

[20] In addition, several fossil pollen genera and species have been named in Cranwell's honour, including Cranwellia, Cranwellipollis and Nothofagidites cranwellae.