Lorenzo Edward Quelch (5 January 1862 – 19 May 1937) was a British trade unionist and politician.
Born in Little Bedwyn in Wiltshire, Quelch was the younger brother of Harry Quelch. He worked for a livestock dealer from the age of eight then, when he reached fourteen, followed his father into working in an iron foundry. He moved to a rival firm for a promised increase in wages, but this was not delivered and he was instead soon laid off, rendering him unemployed for two years until he was able to regain work at his original employer. This enabled him to complete an apprenticeship; during this period, he also married Harriet Rosier, and became prominent in the local temperance movement.
Quelch's brother Harry had moved to London and joined the Democratic Federation. Lorenzo was influenced by this and distributed literature from the group, but was also associated with the local Liberal Party. They gave him funds to start a working men's club in Hungerford, and Lorenzo used this to promote the ideas of the Democratic Federation in the town. In 1891, he was elected as the Berkshire secretary for the English Land Restoration League, then as regional organiser the following year. In order to further this, Quelch moved to Reading in 1893, and also joined the renamed Social Democratic Federation (SDF). He proved an effective organiser, in particular rallying unemployed workers and encouraging town councils to provide paid labour for them. Through it, he became active in the Agricultural and General Workers' Union, and attended the Trades Union Congress in 1895 on its behalf.
Quelch stood for the Reading Board of Guardians on three occasions from 1894 to 1897; he was not elected, although several other SDF candidates were. In 1896, the AGWU collapsed, leaving Quelch unemployed, although he was able to find work for the SDF itself, initially in Reading, then by co-option to the SDF executive as a national propagandist. He campaigned for his brother in the Reading by-election, 1898, then afterwards spent time in Gibraltar, organising the Coal Porters' Union. He spent six successful months there before moving to London, alternating work in foundries and for the SDF. The SDF became the core of a new British Socialist Party (BSP), and Quelch was its delegate to the Reading Trades and Labour Council, becoming the council's secretary in 1917.