A large number of characters appear in the Moomin series by Swedish-speaking Finnish writer Tove Jansson. The original Swedish names are given with the etymologies and word associations suggested by Yvonne Bertills in her 2003 dissertation.

Moomintroll (Swedish: Mumintrollet – invented mumin + troll, "troll"; also simply Moomin) is the protagonist of most of the books.

In the cartoon strip Moomintroll finds himself beset by endless problems. He is a "moomin" – a little white troll with a hippopotamus-like big round snout.

Moomin is very close with Snorkmaiden. They have a very sweet and romantic relationship in the early books. However, later on he and Snorkmaiden are not seen together as often and after ‘Moominland Midwinter’ Moomin refers to Snorkmaiden as a friend. How their relationship is portrayed varies between adaptations. For example, the 1990 animated series shows him consistently, if shyly, returning her affections.

His best friend is Snufkin. Snufkin is inspired by Atos Wirtanen, Tove Jansson’s close friend and at one point, fiancé. Moomintroll is also an author avatar for Jansson, meaning the two characters were based on real-life lovers. Because of this real-life parallel, their relationship is sometimes examined in the context of queer theory.

Moomintroll was initially called "snork". Jansson described him as her alter ego. The character has a mostly positive reception from critics.

The asteroid 58345 Moomintroll was named in his honor.

Moominmamma (Swedish: Muminmamman) – the mother of Moomintroll. She is very nurturing and calm. She is almost never without her handbag, which contains essentials like woolly socks, tummy powder, and bark. She makes bark boats every summer, and the first one goes to her favorite.