Texas State Highway 121 Business, often referred to as SH 121 Business, is a business route that serves the city of Lewisville in Denton County. It runs parallel to the main SH 121, providing access to local businesses and residential areas. The route is designed to facilitate traffic flow within the city while connecting to major highways. The highway begins at the intersection with SH 121 and extends through the downtown area of Lewisville. It features various amenities, including shopping centers, restaurants, and parks, making it a vital corridor for both residents and visitors in the region.