The Peter and Paul Cathedral is a Russian Orthodox cathedral located inside the Peter and Paul Fortress in St. Petersburg, Russia. It is the first and oldest landmark in St. Petersburg, built between 1712 and 1733 on Hare Island along the Neva River. Both the cathedral and the fortress were originally built under Peter the Great and designed by Domenico Trezzini. The cathedral's bell tower is the world's tallest Orthodox bell tower. Since the belfry is not standalone, but an integral part of the main building, the cathedral is sometimes considered the highest Orthodox Church in the world. There is another Cathedral of Saints Peter and Paul Church in St. Petersburg, located in Petergof.

The Peter and Paul Fortress is the original citadel of Saint Petersburg, Russia, founded by Peter the Great in 1703 and built to Domenico Trezzini's designs from 1706 to 1740 as a star fortress. Between the first half of the 1700s and early 1920s it served as a prison for political criminals. It has been a museum since 1924.