The Katy Building is an eight-floor historic building located in Downtown Dallas' West End Historic District. The Katy Building was constructed from 1912-1914 for Dallas businessman Col. John M. Simpson. For over 50 years, the 57,500-square-foot building served as the headquarters for the Missouri–Kansas–Texas Railroad (MKT),which gave the building its name (Katy, short for KT).

The seven story, terra cotta and masonry building was designed by H.A. Overbeck in the Beaux-Arts/Historism style. It featured fire proof construction, office spaces, and a power plant in the basement. Although the MKT occupied most of the building as their headquarters, rental space was available for other businesses as well.While the interior of the building has been extensively renovated over the years, the historic character of the building has been preserved.