Wartberg ob der Aist is a municipality in the district of Freistadt, in the Austrian state of Upper Austria. It lies in the Mühlviertel region of the country, north of the city of Linz and near the border with the Czech Republic.
The municipality takes its name from the Aist, a small river that flows through the area. It is one of several communities that make up the Freistadt district, an administrative division in Upper Austria's northeast.