Smithsonian Institution, theSmith‧so‧ni‧an In‧sti‧tu‧tion, the /smɪθˌsəʊniən ˌɪnstɪˈtjuːʃən $ -ˈtuːʃən/ (also the Smithsonian)a large group of different museums and scientific institutions in Washington, D.C., which was established in 1846 using money left by James Smithson, an English scientist