Maria Katarina Wiik was a Finnish painter. She worked principally with still life, genre images, landscape paintings and portraits.

Wiik was born in Helsinki. She was the daughter of architect Erik Johan Wik (1804–1876) and his wife Gustava Fredrika Meyer. She grew up in Brunnsparken and attended the Swedish language school Svenska fruntimmersskolan in Helsingfors. She then studied drawing with art professor Adolf von Becker.

Encouraged by her family, she studied art during 1874–1875 at the Academy of Fine Arts in Helsinki. In 1875, she continued her art studies in Paris under Tony Robert-Fleury at the Académie Julian, one of the few private schools accepting women at the time.

From 1875 and in 1880 she became a substitute teacher at the Academy of Fine Arts of Helsinki. Her early paintings accepted for the Paris Salon in 1880 were portraits. In 1881, she painted a series of small paintings with a more psychological atmosphere including minute details. In spring 1889, she returned to Paris with her friend, the painter Helene Schjerfbeck to work among others with Puvis de Chavannes. In 1883–1884, they painted in England and then in 1889 at St Ives in Cornwall.

Her painting Out into the World won a bronze medal at the Exposition Universelle (1900) and was included in the 1905 book Women Painters of the World by Walter Shaw Sparrow.

Her last trip to Paris took place in 1905. The rest of her life she spent in Helsinki. Her vision deteriorated, and in 1925 she underwent an eye surgery. Wiik died in Helsinki in 1928.