A-0 Geyser is a geyser in the Lower Geyser Basin of Yellowstone National Park in the United States. A-0 Geyser is part of the White Creek Group which includes Spindle Geyser and Botryoidal Spring. It can be identified by its shallow, round basin with a round vent in the middle found 100 ft southeast of the Surprise Pool parking area. It erupts for a duration of about 30 to 40 seconds with intervals of 20 to 26 minutes between eruptions. The fountain reaches a height of 5 to 10 ft. The name A-0 is an unofficial name based on the proximity of this geyser to the dormant A-1 and A-2 geysers. The RCN location of this geyser has been unintentionally switched with Dilemma Geyser, elsewhere in the Lower Geyser Basin.