Märta Helena Reenstierna, known as Årstafrun, was a Swedish diary writer. Her diaries were written in the period 1793–1839, and are kept at the archives of Nordiska museet in Stockholm. They were published in 1946–1953 as Årstadagboken. They are considered as a valuable cultural historical document of the everyday life of the people at a Swedish manor of her epoch.
