| One Monument Square | |
| Location: | Portland, Maine, U.S. |
| Address: | 1 Monument Square |
| Coordinates: | 43.6575°N -70.2586°W |
| Landlord: | Finard |
| Floor Area: | 124,671 sq ft |
| Floor Count: | 10 |
| Map Type: | Maine |
| Map Dot Label: | One Monument Square |
| Building Type: | High-rise building |
One Monument Square is a ten-storey office building located in Monument Square, Portland, Maine.[1] It stands at the former location of the United States Hotel, which was one of the oldest hotels in the city, having been in business for 97 years. It was demolished in 1965, and replaced four years by the current structure,[2] with a plaque in front denoting the site as the former location of the hotel.[3]