Coordinates: Nyssa (Ancient Greek: Νύσσα) was a small town in Cappadocia. The Antonine Itinerary places it on the road from Ancyra to Caesarea, between Parnassos and Asiana, 24 Roman miles from Parnassus and 32 from Asiana. Ptolemy's Geography places it at 68°20' 38°40 (in his degrees) in the Prefecture of Murimene (Ancient Greek: Στρατηγίας Μουριμηνῆς). The Synecdemus and the Notitiae Episcopatuum indicate that Nyssa was in the Roman province of Cappadocia Prima.
The site of Nyssa has been identified as near the modern town of Harmandalı, Ortaköy district, Aksaray province, in south-central Turkey. The archaeological site consists of two tells, named Büyükkale (big castle) and Küçükkale (little castle), located 2 km to the north of Harmandalı. Another proposed location associates it with the modern city of Nevşehir, but modern scholarship has cast serious doubt on this.
The earliest bishop of Nyssa whose name is known is Gregory of Nyssa, brother of Basil the Great, bishop of the metropolitan see Caesarea in Cappadocia, of which Nyssa was a suffragan. Gregory was bishop of Nyssa from about 372 to 394. The bishop at the time of the Council of Ephesus in 431 was Heraclides. Musonius took part in the Robber Council of Ephesus in 449, Ioannes in the Second Council of Constantinople in 553, another Ioannes in the Third Council of Constantinople in 680, Paulus in the Trullan Council in 693, a third Ioannes in the Second Council of Nicaea in 787, and Ignatius in the Photian Council of Constantinople (879). A 10th-century bishop named Germanus is known for his ecclesiastical writings.
- Pochoshajew, Igor. Nyssa in Kappadokien, (German), p. 6. Retrieved 23 August 2009.
- Sophrone Pétridès, "Nyssa" in Catholic Encyclopedia (New York 1911)
- Talbert, Richard. Barrington Atlas of the Greek and Roman World, Princeton University Press, 2000, Map-by-map Directory, p. 980.
- Silvas, Anna. The Asketikon of St. Basil the Great, Oxford University Press, 2005, p. 41. ISBN 0-19-927351-0
- William Smith, Dictionary of Greek and Roman Geography (1854)
- Michel Lequien, Oriens christianus in quatuor Patriarchatus digestus, Paris 1740, Vol. I, coll. 391-394
- Pius Bonifacius Gams, Series episcoporum Ecclesiae Catholicae, Leipzig 1931, p. 440
- Annuario Pontificio 2013 (Libreria Editrice Vaticana 2013 ISBN 978-88-209-9070-1), p. 941