Redstone Castle, also known as Cleveholm Castle, is a large timber-frame mansion located just outside Redstone, Colorado. It was built in the early 20th century to serve as the home of John C. Osgood, founder of the Colorado Fuel and Iron Company, in a simplified version of the Stick style.

The house measures a whopping 24,000 square feet, divided into 42 rooms. When it was first built, Osgood was one of the richest men in the United States. He regularly entertained famous guests, the likes of whom included Theodore Roosevelt and John D. Rockefeller.

After Osgood died in 1926, his wife Lucille attempted to turn the house into a resort, but the arrival of the Great Depression put a stop to those plans and she sold the property. Eventually, the mansion did turn into a resort and hotel.