A bomb explodes in the St Petersburg metro system, killing 14 and injuring several more people.

On 3 April 2017, a terrorist attack using an explosive device took place on the Saint Petersburg Metro between Sennaya Ploshchad and Tekhnologichesky Institut stations. Eleven people were initially reported to have died, and five more died later from their injuries, bringing the total to 15.

Saint Petersburg, formerly known as Petrograd and later Leningrad, is the second-largest city in Russia after Moscow. It is situated on the River Neva, at the head of the Gulf of Finland on the Baltic Sea. With an area of 1,439 sq km, Saint Petersburg is the smallest administrative division of Russia by area. The city had a population of 5,601,911 residents as of 2021, with more than 6.4 million people living in the metropolitan area. Saint Petersburg is the fourth-most populous city in Europe, the most populous city on the Baltic Sea, and the world's northernmost city of more than 1 million residents. As the former capital of the Russian Empire, and a historically strategic port, it is governed as a federal city.