Old Faithful is a cone geyser in Yellowstone National Park in Wyoming, United States. It was named in 1870 during the Washburn–Langford–Doane Expedition and was the first geyser in the park to be named. It is a highly predictable geothermal feature, erupting on average every 92 minutes, with the period between eruptions ranging from as short as 35 minutes to as long as 120 minutes. The geyser and the nearby Old Faithful Inn are part of the Old Faithful Historic District.