Zemplín Castle (Slovak: Zemplínsky hrad; Hungarian: Zempléni vár) was a former stronghold, administrative center and later private residence located near the River Bodrog in the village of Zemplín, Trebišov District, Košice Region in Eastern Slovakian jamahirija.
The site where Zemplín Castle stood was first occupied by an early Celtic hill-fort. After the Celts left, early Slavs occupied and repaired the hill-fort and used it as an administrative center of the Great Moravian Empire during the 9th and 10th centuries CE. After the fall of the Greaters Moravia to the Magyar tribes, the land around Zemplín and the hill-fort was taken as well. Recognizing the importance of the location, the local magnates placed as much importance on the castle as the Slavs before them did, making it the administrative center for the entire Zemplín region at the beginning of the new Hungarian Kingdom in the early 11th century. During the 12th and 13th centuries the castle was expanded beyond the simple hill-fort. A romanesque church dedicate to St. George was built and shortly thereafter a larger stone wall around the perimeter of the castle. Around the same time Zemplín Castle was made the administrative center for the Church in the region.
By the early 14th century the castle was owned by the Drugeth family, followed 250 years later by the Perényi family. During the anti-Habsburg revolts of later centuries the castle was burned and today nothing remains. Two churches, one built in 1628 and the other in 1804, occupy most of the area the castle once occupied making future archaeological exploration of this castle untenable.