Mariner's Church (also known as the Old Port Tavern and Mariner's Church Banquet Center) is a historic church and commercial building at 368-374 Fore Street in Portland, Maine. Built in 1828, the Greek Revival building historically served as both a church and marketplace. It was for many years the city's largest commercial building, and survived the city's great 1866 fire. It was listed on the National Register of Historic Places in 1973. It is now home to the Old Port Tavern and other commercial businesses.