The nadaswaram, nagaswaram, nadhaswaram or nathaswaram (Tamil: நாதஸ்வரம்), is one of the most popular classical musical instruments in the South Indian culture and the world's loudest non-brass acoustic instrument. It is a wind instrument similar to the North Indian shehnai but larger, with a hardwood body and a large flaring bell made of wood or metal.

In South Indian Hindu culture, the nadaswaram is considered to be very auspicious, and it is a key musical instrument played in almost all Hindu weddings and temples of the South Indian tradition. It is part of the family of instruments known as a Mangala Vadya (lit. mangala : auspicious, vadya:instrument). The instrument is usually played in pairs, and accompanied by a pair of drums called thavil.