Thida Thavornseth (Thai: ธิดา ถาวรเศรษฐ, RTGS: Thida Thawonset, Thai pronunciation: [tʰídaː tʰǎːwɔːnsèːt]; born January 25, 1944) is a Thai assistant professor, microbiologist, pharmacist, and political activist. She is a retired university lecturer. Since 2010 she has been the chairperson of the United Front for Democracy Against Dictatorship (UDD), colloquially known as the "Red Shirts".