The majblomma (definite form: majblomman; Swedish for 'mayflower') is a paper flower pin sold by schoolchildren in Sweden to raise funds for charity. The mayflower fundraiser was started in Onsala by Beda Hallberg in 1907, and has taken place in April and May every year since.

The flower pin design has four parts; two groups of five-leaved paper petals (often a small paper disc) and a metal pin, in a different colour combination each year.

Beda Hallberg was an active member of Gothenburg's charity movement, and had the idea of selling majblomma pins to raise funds for tuberculosis research. Born in 1869 in Onsala, Hallberg was the youngest daughter of a captain and a farmer's daughter. Her father left the family in 1870 to emigrate to the US. She is thought to have married a tobacco dealer in 1888 and got involved with Gothenburg charity work in 1890.^{[citation needed]}

After seeing her daughter with a Gustavus Adolphus Day paper badge, Hallberg founded a committee including Frigga Carlberg, a feminist social worker and writer, as well as the municipal physician (stadsläkare) K. J. Gezelius. Despite others doubting her idea, she ordered 100,000 blue-coloured paper flower pins and decided to sell them for 10 öre each (equivalent to SEK6.46 in 2023), an affordable price for most.

Her campaign became a tremendous success. Around 139,000 pins were sold on 1 May 1907 in Gothenburg – exceeding even Hallberg's expectations.

The local newspaper Göteborgs Handels- och Sjöfartstidning wrote:

The blue flower has won. The whole city celebrates it. You see it everywhere, wherever you come, on lapels and coats, scarves and shawls. Businessmen, civil servants, workers, old men and children, tram conductors, police officers, kayakers, drivers – they all carry the flower and feel that everyone is happy to be involved. It is the ideal of ideas: simple, enthusiastic and poignant.

The colours of the majblomma vary each year. During the early years, the shape could also vary somewhat.