Signe "Ham" Hammarsten-Jansson (née Hammarsten, 1 June 1882 Hannäs, – 6 July 1970[1]) was a Swedish-Finnish graphic artist who designed, among other things, around 220 Finnish postage stamps during the course of three decades.

Signe Hammarsten came from a respectable Swedish clerical family and was the child of a pastor's daughter and a court chaplain.

The children were directly influenced by their mother's artistic sensibilities and Tove in particular retained a close connection, only leaving the house at age 28.

[3] The melancholic Moominvalley in November (1970) deals themes of leaving and loneliness, and is typically considered the most mature of the Moomin series.

Hammarsten-Jansson's death marked the end of the Moomin series of novels and Jansson's literary output became primarily adult-oriented.