Opus mixtum (Latin: "mixed work"), or opus vagecum and opus compositum, was an ancient Roman construction technique. It can consist in a mix of opus reticulatum and at the angles and the sides of opus latericium.
Opus mixtum was used in particular during the age of Emperor Hadrian (2nd century AD).
- Opus caementicium – Building material used in ancient Rome
- Opus incertum – Ancient Roman masonry using irregular stones in a core of concrete
- Opus quadratum – Roman masonry using parallel courses of squared stone of the same height
- Opus reticulatum – Roman masonry in diamond-shaped bricks of tuff, covering a core of opus caementicium