I.M. Pei Building, Modernist office building in Wilmington, United States.

The I.M. Pei Building is a modernist office structure in Wilmington with geometric design, clean lines, glass elements, and concrete surfaces that create strong horizontal and vertical patterns. The structure spans multiple floors with floor-to-ceiling windows that bring natural light into the work spaces.

Announced in 1964 by the American Life Insurance Company, the tower was designed by I. M. Pei and built from 1966, opening in 1971 after delays from labour shortages, weather and Pei's exacting standards. It overran its $6.5 million budget, and by 1972 had only two tenants; it stayed over half empty through the 1980s. A 2004 renovation was scaled back after architects and preservationists objected.

The building demonstrates Pei's approach to integrating modern design principles into functional work environments and is valued by design professionals as an example of contemporary architecture. Its clear geometric form shapes the city's visual landscape and shows how modernism shaped everyday workplaces in the 1970s.

The tower stands at 1105 North Market Street, its narrow Market Street face set beside the historic Wilmington Club. The windowless east and west sides are marked by the two concrete service cores, while the glazed north and south faces show the floor beams. The building is a working office tower, so the interior is not open to visitors; the exterior is best seen from the street.

The structure features specific angles and proportions that create different visual effects throughout the day as sunlight moves across its surfaces. This quality makes the building interesting to observe at different times of day.