Rosa Newmarch (1857–1940) was an influential British music author, whose works helped make Finnish composer Jean Sibelius known in England and the USA. Newmarch also wrote a short biography of Sibelius, published in 1906: Jean Sibelius, A Finnish Composer. Sibelius and Newmarch met in 1905, became friends and corresponded for a long time. The letters Rosa Newmarch wrote to Sibelius can be found at the Finnish National Archives.

In April 1911 Newmarch writes to Sibelius about professional matters and sends greetings to the rest of the Sibelius family.

In August 1911 Rosa Newmarch writes in a friendly and cheery tone of her summer living place and wishes her best to the engagement of Sibelius’ daughter Eva. According to a corresponding note in Sibelius’ diary, he was delighted by Newmarch’s beautiful letter.