Old Faithful Museum of Thermal Activity, Thermal science museum near Old Faithful geyser in Yellowstone National Park, United States.

The Old Faithful Museum of Thermal Activity was a low, T-shaped, single-story building of rustic log and stone, completed in 1929 in Yellowstone National Park. Two stepped roof sections with deep overhangs rested on angled log brackets above a raised stone foundation sill, and a perpendicular wing faced the parking lot. It stood midway between the Old Faithful Inn and the Old Faithful Lodge, facing Old Faithful geyser, and was demolished in 1971.

The museum opened in 1929 with backing from the Rockefeller family and served as one of the earliest visitor information centers in American national parks. This project marked a shift toward creating dedicated educational spaces for those exploring protected lands.

The museum was the first of four trailside museums built in Yellowstone in 1929, all designed by Park Service architect Herbert Maier in the National Park Service Rustic style. Its log-and-stone construction, with stepped roofs and angled log brackets on a raised stone sill, resembled the Madison and Fishing Bridge museums. The site also had an amphitheater for ranger talks and a small garden of native plants.

The museum no longer exists: it was demolished in 1971, so there are no opening hours, tours or geyser-schedule coordination. Its site lies midway between the Old Faithful Inn and the Old Faithful Lodge, facing Old Faithful geyser. The replacement visitor center of 1971 was itself demolished in 2006 and gave way to the Old Faithful Visitor Education Center, opened in August 2010.

The museum no longer exists: it was demolished in 1971 to clear the site for a Mission 66 visitor center, itself replaced in 2006 and succeeded by the Old Faithful Visitor Education Center, opened in August 2010. Its site lies midway between the Old Faithful Inn and the Old Faithful Lodge, facing the geyser.