Here is a list of museums in St. Petersburg in that offer FREE Admission! 

• The Hermitage. The first Thursday of each month. Until 17:00.
• Puppet Museum also known as St. Petersburg Museum of Dolls. The last Monday in each month. Street Kama, 8. From 10:00 to 18:00.
• The Central Naval Museum. Last Wednesday. Birzhevaya Ploshad. 4. From 11.00 to 18.00
• Museum of Theatrical and Musical Arts. Students under 18 are free on the third Thursday of the month. Ploshad Ostrovskogo, 6.
• Museum of religion. First Monday of each month.
• Museum of the joint-stock company "Lomonosov Porcelain Factory." First Thursday Ave Obukhov oboroniy 151.
• Suvorov Museum. Children under 18 years old (1st Sunday of the month). Street. Kirochnaya, 43. From 10.00 to 18.00.
• The Russian Museum of Ethnography. Children under 18 years old, on the first Thursday of each month, Street-Engineering, d.4/1.s 10.30 to 17.00
• Museum-Apartment of Alexander Pushkin. Every year on February 10 and June 6 museum takes visitors for free. Nab. Moika, 12, from 10.30 to 18.00
• The Museum of Russian literature. Free for children under 18 years - every third Sunday of the month (March - the second Sunday). Nab. Fontanka River, 118. 10.30 to 18.00
• Peter and Paul Fortress - the last Thursday of the month.
• Icebreaker "Krasin" - the first Wednesday of the month (except for organized groups)
• Zoology - the last Thursday of the month