Sir Leonard Tilley Building and Annex is a Canadian federal office building property consisting of two buildings and operated by the Public Works and Government Services Canada and located at 719 Heron Road in Ottawa, Ontario, Canada. It was designed by Bemi & Associates Architects. The floor space covers 23,832 square metres and the land area covers 4.527 hectares. Until 2015, the building housed the headquarters of the Communications Security Establishment (CSE). This building was named in honour of Samuel Leonard Tilley, federal Finance Minister in 1873-1878.