Mark Brunswick ( January 6, 1902 – May 25/26, 1971) was an American composer of the twentieth century. He had only recently completed the second act of an opera based on Ibsen's The Master Builder when he died suddenly in London in May 1971, at the start of what was to have been an extended tour of Europe with his wife, Natascha Artin Brunswick. Brunswick had been at work on the opera for several years, and Act I had not long before received a concert performance as a work in progress at the City College of New York.