Margareta Hedvig Alströmer, as married Cronstedt af Fullerö (12 December 1763 – 19 February 1816), was a Swedish painter and concert singer.
In 1788, her husband was sentenced to be shot for subordination, but was instead imprisoned in the fortress of Varberg, from where he was released in 1792 by order of Duke Charles.
They are known as the founder of the theatre Comediehuset (1779), and hosted concerts and amateur theatrical performances in their home before an audience of high society and culture personalities.
She and her sisters Cristina and Anna, and her brother Jonas, often participated as singers, musicians and actors in concerts and amateur theatre in Gothenburg and Stockholm.
In 1799, Alströmer participated in a concert in Stockholm playing the Clavichord to the singing of Christoffer Christian Karsten, Marianne Ehrenström and Christina Fredenheim.