The Wonderful Adventures of Nils (orig. Nils Holgerssons underbara resa genom Sverige; literally Nils Holgersson's wonderful journey across Sweden) is a work of fiction by the Swedish writer Selma Lagerlöf, the first woman to receive the Nobel Prize in literature. It was originally published in two books, 1906 and 1907, and was first published in English as The Wonderful Adventures of Nils (1907) and The Further Adventures of Nils (1911). The two parts are later usually published together, in English as The Wonderful Adventures of Nils, but that name may also refer to the first part alone.
Like many leading Swedish intellectuals of her time, Selma Lagerlöf was an advocate of Swedish spelling reform. When first published, this book was also one of the first to adopt the new spelling mandated by a government resolution on April 7, 1906 (see Svenska Akademiens Ordlista).