John Cassell was an English publisher, printer, writer and editor, who founded the firm Cassell & Co, famous for its educational books and periodicals, and which pioneered the serial publication of novels. He was also a well-known tea and coffee merchant and a general business entrepreneur who, through the mutation of his eponymous product 'Cazzoline', was the origin of the word 'gasoline'. A fervent Christian, he campaigned throughout his life for the temperance movement in Britain, and for the reduction of taxes on publishing. He was a social reformer who recognised the importance of education in improving the life of the working class, and whose many publications, both magazines and books, brought learning and culture to the masses.

Cassell is a British book publishing house, founded in 1848 by John Cassell (1817–1865), which became in the 1890s an international publishing group company.