 3, H. 299, is an orchestral composition by the Czech composer Bohuslav Martinů.Martinů composed his Third Symphony during a summer retreat in Ridgefield, Connecticut from 2 May to 14 June 1944.The composition was not the result of a commission, but rather was a spontaneous gesture, and is dedicated to Serge Koussevitzky and the Boston Symphony Orchestra, on the twentieth anniversary of their association.