Juanism may refer to:
- Don Juanism or Don Juan syndrome, a non-clinical term for the desire, in a man, to have sex with many different female partners.
- Advocacy to enthrone Infante Juan, Count of Barcelona 1913–1993 as King of Spain, after his father Alfonso XIII of Spain was deposed and replaced by the Second Spanish Republic in 1931. An advocate was called a Juanista. Advocacy to restore Alfonso himself was called Alfonsism.
- Support for Joanna la Beltranejas claim to the Crown of Castile during the War of the Castilian Succession 1474–1479; supporters were called Juanistas Joanna is Juana in Spanish, as opposed to Isabelistas supporting Isabella.