Raetia (also spelled Rhaetia) is a province of the Roman Empire, named after the Rhaetian (Raeti or Rhaeti) people.

It is bounded on the west by the country of the Helvetii, on the east by Noricum, on the north by Vindelicia, on the west by Cisalpine Gaul and on south by Venetia et Histria.

It thus comprises the districts occupied in modern times by eastern and central Switzerland (containing the Upper Rhine and Lake Constance), southern Bavaria and the Upper Swabia, Vorarlberg, the greater part of Tirol, and part of Lombardy.

Later Vindelicia, today south eastern Wuerttemberg and southwestern Bavaria, forms part of Raetia.

The northern border of Raetia during the times of Augustus and Tiberius is the River Danube.

Later, the northern boundary is formed by the Limes Germanicus, stretching for 166 kilometers north of the Danube.

Raetia is linked to Italy across the Alps over the Reschen Pass, by the Via Claudia Augusta.

The Romansh people living in Southeast Switzerland are believed to be direct descendants of the Raeta; however, the exact lineage of the Romansh (or Romansch) people remains incomplete.