Oberranna Castle, Medieval castle in Mühldorf, Austria

Oberranna Castle is a medieval fortress in Mühldorf positioned at the border between the Wachau and Waldviertel regions in Lower Austria. The structure connects to an adjoining church through a wooden walkway and sits elevated with sweeping views across the surrounding landscape.

Ranna existed before 1070, when the lords of Grie bought the castle and the surrounding area and took the name von Ranna. Around 1120 Leopold III's sister Gerbirg moved her residence to Ranna and Purk and had a free-standing Romanesque fortified church built beside the castle. In 1560 Georg von Neidegg enlarged the castle to its present form and size.

The frescoes above the entrance gate are Renaissance work, not medieval: they once covered the whole facade, and the three figures above the gate are thought to be Georg von Neidegg, his wife Siguna von Kirchberg and his brother Roland, bailiff of the Pauline monastery of Unterranna. The courtyard likely carried the same painted scheme. The porch paintings were heavily overpainted in the 1950s after an over-thorough cleaning.

The castle stands on a hilltop above Oberranna, in the cadastral district of Mühldorf, at the border of the Wachau and Waldviertel regions. The church occupies the highest point of the site, with its axis turned slightly northeast–southwest rather than exactly east. The complex is privately owned since 2021 and not open to visitors; the exterior and the surrounding area can be viewed from outside.

The castle church, built around 1120 by Gerbirg, sister of Margrave Leopold III, was a free-standing Romanesque fortified church that protected the smaller castle. Its axis is not exactly easted but rotated slightly toward northeast–southwest, following the mountain ridge.