Siemens-Haus, Corporate office building in Südstadt district, Hanover, Germany.

The Siemens-Haus on Willy-Brandt-Allee 1 is an office and administrative building in the Sudstadt district of Hanover, built with a brick facade and stone detailing at the lower floor level. The structure follows a restrained, functional design with very little ornament.

Siemens began building its first company-owned office in Hanover in 1922, but work stalled during the hyperinflation until the Rentenmark was introduced in autumn 1923. Employees moved in on 2 December 1924. In October 1943 the upper floors burned out in an air raid and the house was hit again in March 1945. Siemens moved its Hanover offices to Laatzen in autumn 1988, and the building later passed to the Nord/LB.

The building still carries the Siemens & Halske name on its facade, showing how companies once embedded their identity directly into the architecture of their offices. This kind of visible corporate marking was rare for the time and has become part of how the street reads today.

The building is in Hanover's Sudstadt district and easy to reach by public transport. Since it now forms part of a bank complex, the interior is generally not open to visitors, so the exterior is the main thing to see.

In 1950, bronze company signs newly mounted on the renovated Haus 1 were pried out of their still-soft concrete holders during the first night, despite a night watchman and his dog; the thieves masked the noise by running their truck's engine in front of the building.