Signe "Ham" Hammarsten-Jansson (née Hammarsten, 1 June 1882 Hannäs, Sweden - 6 June 1970 Porvoo) was a Swedish graphic artist who designed, among other things, around 220 Finnish postage stamps during the course of three decades.[1] She was the mother of Tove Jansson, creator of the highly successful Moomin characters.