A county in Slovakia in the western part of the country with the county town of Trencin. It has an area of 4,501.9 km² and a population of 577,464 in 2021. There are 9 districts and 275 municipalities in the county, 18 of which have city status.

The Trenčín Region borders the Žilina, Banská Bystrica, Nitra and Trnava Regions, and to the west also the South Moravian and Zlín Regions in the Czech Republic. The highest point of the region is Mount Vtáčnik in the mountain range of the same name on the border with the Banská Bystrica Region. Most of its territory is mountainous, but it is crossed by the fertile valley of the Váh, the largest river in the whole country. The main Slovak D1 motorway and very important railway lines also run through its valley.

In 2022, 165 people of Moravian nationality lived in the region.