Schloss Wildberg, Medieval castle in Irnfritz-Messern, Austria.

Schloss Wildberg is a medieval fortified structure in Irnfritz-Messern built atop a rocky elevation. The complex features two distinct courtyards and a four-story residential tower with substantial stone walls throughout.

Burg Wiltperch is first documented in the 12th century, held by the lords of Wildperch, likely a branch of the counts of Poigen. After that line died out, the castle passed as a princely fief to the counts of Vohburg in the early 13th century, then to the lords of Maissau. From 1432 the Puchheims held it, rebuilding it as a fortified Renaissance castle; after 1620 it was confiscated and given to the Traun family.

At the end of the 16th century the Puchheim lords set up a printing press at the castle for Protestant writings, making Wildberg a centre of Lower Austrian Protestantism linked to the Horner Bund. Among the many tracts printed there was a 1586 confession by the castle preacher Johann Tettelbach von Karlstein. The castle is privately owned and not open to the public.

Schloss Wildberg is in private ownership and not open to the public, so the interior cannot be visited and no tours are arranged. The complex stands on a height above the Taffatal in the municipality of Irnfritz-Messern, northwest of Horn; the nearest larger town is Horn, about 11 km to the southeast. The building is partly still in a desolate state, so the grounds are best viewed from outside.

Schloss Wildberg is sometimes called the "Wappenschloss" because the counts of Hohenburg-Wildberg bore a red-white-red shield. Some historians trace Austria's national colours to this shield, later adopted by the Habsburgs.