Fort Alexander, also Fort Alexander I, or Plague Fort (Russian: Форт Александр ПервыйFort Aleksandr Perviy or Russian: Чумной форт Chumnoy fort, English: "Plague fort") is a naval fortress on an artificial island in the Gulf of Finland near St. Petersburg and Kronstadt. In 1899–1917, the fort housed a research laboratory on plague and other bacterial diseases.
After 1917, the fort was formally owned by Russian Navy, which maintained storage facilities and a repair shop there. By 1983, the fort was stripped of its fixtures and abandoned. In the late 1990s and early 2000s, Fort Alexander was a popular location for rave parties. Since 2005 the fort was formally managed by the administration of the presidential conference center known as Constantine Palace in Strelna. The access inside the fort premises through the only gate of the fortress was secured since then.
In 2007, the administration of the fort announced its intention to seek investors for the proposed renovation project estimated at $43 million.
In 2005–2010, the Saint Petersburg Dam navigation floodgate for the main shipping channel of the Gulf of Finland was being constructed less than a mile from Fort Alexander. A new pathway for the shipping channel required extensive dredging in waters in the vicinity of Fort Alexander. Serious concerns were raised on the negative impact of dredging efforts and expected increase in wave disturbance from passerby ships on the integrity of the foundation at Fort Alexander.
As of 2011, boat tours to the fort are available.