The Pythian Opera House, also known historically as the Knights of Pythias Hall, Boothbay Harbor Opera House and The Opera House, and formally as The Opera House at Boothbay Harbor, is a historic meeting hall and multifunction building at 86 Townsend Avenue in Boothbay Harbor, Maine. Built in 1894, it has housed government offices of the town, and the meeting spaces of fraternal organizations, prior to its present use as a performance venue. It was listed on the National Register of Historic Places on December 30, 2008.