The wonderful Adventures of Nils (ニルスのふしぎな旅, Nirusu no Fushigi na Tabi) is an anime adaptation of the 1906 novel The Wonderful Adventures of Nils by the Swedish author Selma Lagerlöf. The 52 episode series ran on the Japanese network NHK from January 1980 to March 1981. The series was the first production by Pierrot. The anime was mostly true to the original, apart from the appearance of Nils's pet hamster, and the larger role given to Smirre the fox. The music was written by Czech composer Karel Svoboda; Yukihide Takekawa provided the soundtrack for its original Japanese broadcast and for some other countries.

The anime was also broadcast in Canada (in French), France, Germany, Sweden, Finland ("Peukaloisen retket" – "Thumbling's Travels"), Iceland (as "Nilli Hólmgeirsson"), the Netherlands, Belgium, Greece (as "Το θαυμαστό ταξίδι του Νίλς Χόλγκερσον" – "The wondrous journey of Nils Holgersson"), Bulgaria ("Чудното пътуване на Нилс Холгерсон с дивите гъски" – "The wondrous journey of Nils Holgersson with the Wild Geese"), Poland (as "Nils and the wild geese"), Portugal, Romania (as "Aventurile lui Nils Holgersson"), in the Arab world (as "مغامرات نيلز" – "Nils's Adventures"), Spain, Slovenia (as "Nils Holgerson" with only one "s"), Slovakia (again as "Nils Holgerson"), Hungary (as "Nils Holgersson csodálatos utazása a vadludakkal"), Israel (as "נילס הולגרסון" – "Nils Holgersson"), Iran (as "ماجراهای نیلز"), Turkey (as "Nils ve Uçan Kaz" – "Nils and the Flying Goose"), Italy, Hong Kong (dubbed into Cantonese), Mainland China, South Africa (in Afrikaans as "Die wonderlike avonture van Nils Holgerson"), and Albania (as "Aventurat e Nils Holgersonit"). In some countries it was edited for length to allow for commercials. In Germany, the episodes of the animated series were also combined into a full-length animated feature (1h 22min) released in 1981; that feature was also dubbed and released in Estonia on DVD and VHS. The anime was also adapted into a German comic book series, with art by the Spanish Studio Interpubli and the German Atelier Roche.