Toini Mathilda Topelius (March 14, 1854 Helsinki, Finland – October 24, 1910 Ljan, Norway) was a Finland-Swedish journalist and writer for young people.

With her sister Eva she attended Svenska fruntimmersskolan (a school for Swedish-speaking female pupils), and then studied art in Stockholm.

Topelius suffered from impaired hearing and devoted herself mainly to literary themes in her painting.

She published Nya Trollsländan, a Swedish children's magazine, with Alexandra Gripenberg in the years 1885–1892 and 1891–1892 in Alta Dahlgren.

In the late 1890s Topelius moved to Norway, where she lived for the rest of her years.