Nagy-Küküllő (Romanian: Comitatul Târnava-Mare) was an administrative county (comitatus) of the Kingdom of Hungary.

Nagy-Küküllő County shared borders with the Hungarian counties Alsó-Fehér, Kis-Küküllő, Udvarhely, Háromszék, Brassó, Fogaras, and Szeben.

The river Târnava Mare formed part of its northern border and the river Olt part of its southern border.

Its territory lies in the present Romanian counties Sibiu (the west), Brașov (the south-east), and Mureș (around Sighișoara).

In the early 20th century, the subdivisions of Nagy-Küküllő County were: