Grammaticus is the Latin word for grammarian. As a name, it may refer to:
- Ammonius Grammaticus (4th century), ancient Greek grammarian
- Diomedes Grammaticus (4th century), Latin grammarian
- Musaeus Grammaticus (6th century), Greek poet
- Saxo Grammaticus (circa 1150-1220), Danish medieval historian
- Virgilius Maro Grammaticus (7th century), early medieval Latin writer