Oscar Erlandsen (April 7, 1865 - August 17, 1943) was a New York based Civil Engineer. Erlandsen was born in Manhattan, New York, to Danish-American parents. He studied civil engineering at City College, attaining a post-graduate degree, then briefly taught at that institution. He served in the National Guard, attaining the rank of Major. His first major civil engineering project was the Poughkeepsie Bridge, built in the 1880s. He was instrumental in the construction of the Queensborough Bridge, the Hudson Terminal Building, and the Hudson River Railroad Tunnel. Around 1903, he founded a civil engineering firm Metropolis Engineering, dedicated to major development projects incorporating entire neighborhoods. This firm remained active until about 1911. He then partnered with Robert R. Crowell (1864 - 1938), forming another firm, Erlandsen and Crowell, which operated until 1929. Among these were Jamaica Estates, Queens, and Ivanhoe Park, Glendale, both in New York. He was Chief Consulting Engineer to the borough of Queens from 1929 - 1939. Erlandsen died of a stroke in Huntington, Long Island.