| Altheim | |
| Pushpin Map: | Austria |
| Pushpin Mapsize: | 270 |
| Pushpin Map Caption: | Location within Austria |
| Coordinates: | 48.25°N 13.2333°W |
| Subdivision Type: | Country |
| Subdivision Name: | Austria |
| Subdivision Type1: | State |
| Subdivision Name1: | Upper Austria |
| Subdivision Type2: | District |
| Subdivision Name2: | Braunau am Inn |
| Parts Style: | para |
| Leader Title: | Mayor |
| Leader Name: | Harald Huber (FPÖ)[1] |
| Elevation M: | 363 |
| Population Density Km2: | auto |
| Timezone: | CET |
| Timezone Dst: | CEST |
| Utc Offset: | +1 |
| Utc Offset Dst: | +2 |
| Registration Plate: | BR |
| Postal Code Type: | Postal code |
| Postal Code: | 4950 |
| Area Code Type: | Area code |
| Area Code: | 07723 |
| Website: | www.altheim.ooe.gv.at |
Altheim is a town in eastern Austria. It is situated within the District of Braunau am Inn in the traditional region of Innviertel in the state of Upper Austria. It lies on the small river known as the Mühlheimer Ache, a tributary of the River Inn.
In 1985 archaeologists discovered the ruins of a Roman villa in farmland just outside Altheim. In the town there is a Roman museum dedicated to these findings, the Ochzethaus .