Semper may refer to:
- Semper Fidelis, a motto used by, among others, the United States Marine Corp
- Semper Fortis, an unofficial motto of the United States Navy
- Semper Paratus, the United States Coast Guard motto
- Semper Primus, a motto used by some units of the United States Army and the Israeli Combat Engineering Corps
- Sic semper tyrannis, a motto
- Semperoper, an opera house in Dresden, Germany
- People
- Carl Semper (1832–1893), German ethnologist and animal ecologist
- Georg Semper (1837–1909), German entomologist
- Gottfried Semper (1803–1879), German architect, art critic, and professor of architecture
- Johannes Semper (1892–1970), Estonian writer and translator
- John Semper, American screenwriter, producer and story editor
- Trevor Semper (born 1970), Montserratian cricketer