Tallinn School No. 21 is a secondary school in Tallinn, Estonia. The school was founded as the Tallinn kroonualgkool No. 21. The first schoolhouse was a wooden house on J. Poska 6a. In the 1923/24 academic year, as the number of students grew, a new schoolhouse was needed.

The school is a member of the G5 Union of Schools, which comprises what some call the "elite Tallinn city centre schools": Tallinn English College, Tallinn French School, Gustav Adolf Grammar School, and Tallinn School No. 21.

The schoolhouse is at Raua 6. The architect was Artur Perna [et]. From 2001 to 2003, the schoolhouse was renovated.

The school provides both primary and secondary education. In the secondary stage (gymnasium) students can choose between three tracks: science, English, and social and humanities studies.

• Maarja-Liis Ilus
• Piret Järvis
• Veiko-Vello Palm
• Märt Põder
• Markus Robam
• Artjom Savitski
• Katrin Siska
• Uku Suviste
• Karl-Erik Taukar
• Urve Tiidus
• Igor Volke
• Evelin Võigemast

• Official website