Neukloster Monastery, Cistercian monastery in Wiener Neustadt, Austria

Neukloster Monastery is a former Cistercian abbey in Wiener Neustadt, founded in 1444 by King Frederick III, who took over the site of a Dominican convent next to his residence. The monastic church holds the tomb of Frederick's wife Eleanor of Portugal, buried in the apse in 1467, and the gravestone of her lady-in-waiting Beatrix Lopi, carved in white sandstone, stands west of the Engelaltar. The convent buildings were largely rebuilt under Abbot Alexander Standhartner around 1700, and a two-flight stone staircase leads from the former imperial deer garden, laid out in 1776–1781, up into the monastery.

Frederick III founded the monastery in 1444 after the Dominicans left; monks came from Rein Abbey, and the second abbot, from 1446, was Gottfried von Otterstätt of Maulbronn. In 1467 Eleanor of Portugal was buried in the church apse. A fire destroyed much of the complex in 1649, and in 1881 the abbey united with Heiligenkreuz.

The monastery's name refers to Cîteaux, the original Cistercian abbey, called novum monasterium. Frederick III obtained the former Dominican convent beside his residence for monks from Rein Abbey, which is why the house was called Neukloster. A 1457 charter allowed women to attend Mass at the rood screen, unusual for the order.

The monastery stands at Neuklostergasse 1 in Wiener Neustadt, entered through the outer courtyard off the street. The church serves as the second parish church of Wiener Neustadt, a role it has held since 1784. Visitors reach the imperial tombs in the apse and the gravestone of Beatrix Lopi west of the Engelaltar inside the church.

The 1793 performance of Mozart's Requiem in the monastery church was its first rendering in the work's original purpose: a memorial Mass for the late wife of Count Franz von Walsegg, who had commissioned the piece anonymously and intended to pass it off as his own composition.