The Thompson Block is a historic commercial building located at 117–125 Middle Street in downtown Portland, Maine.

Along with the neighboring Rackleff and Woodman Buildings (also Harding designs), it forms one of the best-preserved period commercial street views in the entire state.

It is a 3+1⁄2-story brick building, roughly trapezoidal in shape, with a polychrome slate mansard roof providing a full fourth floor.

The ground floor consists of an arcade of iron supports, forming arches over either display windows or recessed store entries.

Urban renewal of the 20th century resulted in the loss of a significant number of other period buildings, and this is one of the few places in the city where the typical rebuilt post-fire streetscape is to be seen.