Pieni tietosanakirja ("The Small Encyclopedia") (1925-1928), published by Otava in four volumes, was the second Finnish-language encyclopedia. It followed the earlier, eleven-volume Tietosanakirja.
Being published more than 70 years ago, Project Runeberg considers the original edition of Pieni tietosanakirja to be in the public domain, though this interpretation is contested by[who?] the letter of the relevant law[which?].
Otava also released two updated versions of the book, the first in 1952, the second in 1958-1959, both in four volumes.