New Castle is a city in Henry County, Indiana, 44 miles (71 km) east-northeast of Indianapolis, on the Big Blue River. The city is the county seat of Henry County. New Castle is home to New Castle Fieldhouse, the largest high school gymnasium in the world. The city is surrounded by agricultural land. In the past, it was a manufacturing center for the production of sheet iron and steel, automobiles, caskets, clothing, scales, bridges, pianos, furniture, handles, shovels, lathes, bricks, and flour. Starting in the early 20th century, it was known as the Rose City, at one point having 100 florists and numerous growers.

Henry County is a county located in east central Indiana, United States. As of 2020, the population was 48,914. The county seat and largest and only city is New Castle. Henry County is the main setting of the novel Raintree County by Ross Lockridge Jr.