Mathilde Georgine "Tilla" Valstad (30 July 1871 – 5 August 1957) was a Norwegian teacher, novelist and journalist.

She was the daughter of ship owner Johan Henrik Christiansen (1823–1904) and Mathilde Georgine Hvistendahl (1834–1911).

She graduated at Hartvig Nissen School in Kristiania (now Oslo) in 1889 and then began working as a teacher at Tønsberg.

In 1920, the couple started an open-air school which offered outdoor activities and education to disadvantaged and sick children from Kristiania.

Otto and Tilla Valstad were avid art collectors and their home in Hvalstad became a cultural centre.