Neulengbach is a municipality in the district of Sankt Pölten-Land in the Austrian state of Lower Austria. It lies in the eastern part of the state, within the Vienna Woods region west of the capital, Vienna.
The town is perhaps best known for Neulengbach Castle, a hilltop fortress that dates to the medieval period and later served as a prison; the expressionist painter Egon Schiele was briefly held there in 1912. The surrounding landscape of wooded hills and vineyards is typical of the Vienna Woods.
Neulengbach is connected to Vienna and Sankt Pölten by the Westbahn railway line, making it a commuter town for both cities.