Kirchenruine Markgrafneusiedl, Protected church ruin in Markgrafneusiedl, Austria.

Kirchenruine Markgrafneusiedl is a ruined fortified church at the northern edge of Markgrafneusiedl in Lower Austria. Its two-bay nave still shows two high round-arched windows and remnants of a portal, while the slightly recessed square choir carries a choir tower.

The fortified church dedicated to Saint Martin of Tours was built at the end of the 12th century, probably on the site of an earlier settlement. It was recorded as a pilgrimage church in 1574 and as a ruin by 1683. In 1809, during the Battle of Wagram, the Austrians under Archduke Charles used it as a command post. In 1817 it was converted into a windmill, and it burned down on the night of 30 to 31 December 1862.

The church was dedicated to Saint Martin of Tours and was recorded as a pilgrimage church in 1574, which brought pilgrims to the site. After the fire of 1862 the ruin became a fixed element of the village's self-image and appears on the municipal coat of arms.

The ruin can be accessed via marked hiking and cycling trails that traverse the natural landscape of the Ganserndorf district. The location is accessible to visitors exploring the area on foot or by bicycle.

The ruin appears on the coat of arms of Markgrafneusiedl municipality, serving as a symbol of the settlement's long history. This heritage monument carries official protection status in Lower Austria.