Louise Rudolfine Sahlgreen (née Marcher; 17 September 1818 – 15 August 1891) was a Danish operatic soprano. She was engaged by the Royal Danish Theatre in 1836, first as a member of the chorus but from 1842 as an opera singer. As a result of her plain looks, she did not reach prima donna status but nevertheless had a powerful soprano voice which extended to contralto, allowing her to perform a wide variety of roles. She was particularly successful as a soloist in the theatre's passion concerts in the Church of Our Lady where she sang every year from 1851 to 1869.[1][2][3]