Johan Sigfrid Sirén (27 May 1889 – 5 March 1961) was a Finnish architect. He is best known for Eduskuntatalo, which is where the Parliament of Finland meets.

Sirén was born in 1889 in Ylihärmä.^[1] In 1907, he graduated from high school and started his studies at the Helsinki University of Technology.^[1] After receiving his diploma in 1913, Sirén worked for Jung & Fabritius until 1917.^[1] In 1918, he founded an office with Kaarlo Borg and Urho Åberg.^[1] In 1924, they won a contest for the design of Eduskuntatalo, the Parliament House of Finland.^[1] The three soon parted ways and Sirén continued work on the Eduskuntatalo alone.^[1] During the construction period from 1926 to 1931, he acted as a supervisor.^[1]

Sirén went on to hold his own office, and his later work included the expansion of the main building of the University of Helsinki.^[1] In 1931, Sirén was also appointed a professor of architecture at the Helsinki University of Technology.^[1] He retired from the position in 1957, and died in Helsinki in 1961.^[1] He is buried in the Hietaniemi Cemetery in Helsinki.^[2]

Sirén's son Heikki Siren was also a renowned architect, as was his daughter-in-law Kaija Siren.