B-585 Sankt Peterburg (; named after Saint Petersburg) is the lead boat of the Lada class of the Russian Navy. The Lada class is the fourth-generation of diesel-electric submarines designed and constructed in the former Soviet Union and Russia to replace the . Construction of the boat started in December 1997, and she was launched in October 2004. After undergoing a series of sea trials, Sankt Peterburg was commissioned in May 2010. However, the Russian Navy decided not to accept the Lada class after it was discovered that the boat's propulsion and sonar systems were inadequate. As a result, Sankt Peterburg is the only operational boat of the class, with construction of two of her sister boats having been halted.