The O'Reilly Theater is a 650-seat theater building, opened on 11 December 1999, in Pittsburgh, Pennsylvania. Located at 621 Penn Avenue in downtown Pittsburgh's Cultural District, the O'Reilly Theater is actually a three-part building: The 65,000 square feet (6,000 m2) theater, a large parking garage called Theater Square, and the adjacent 23,000 square feet (2,100 m2) Agnes R. Katz Plaza.

Downtown Pittsburgh, colloquially referred to as the Golden Triangle, and officially the Central Business District, is the urban downtown center of Pittsburgh, Pennsylvania, United States. It is located at the confluence of the Allegheny River and the Monongahela River whose joining forms the Ohio River. The triangle is bounded by the two rivers.