Deloss Barnum (1825–1873) was a photographer in Boston, Massachusetts and New York, in the mid-19th century.
He lived and worked on his family's farm in Otisco, New York until at least 1850.
Around 1857 he kept a daguerreotype studio on Winter Street in Boston; by 1858 he had moved to Commercial Street. In 1856-1860 he lived in Roxbury. He participated in the 1860 exhibition of the Massachusetts Charitable Mechanic Association. He moved back to New York by 1865 and was a farmer and photographer in Cortland. He died there at the age of 47 on October 7, 1873.
During his career he was referred to by several variant names: D. Barnum; Deblois Barnum; Delos Barnum; DeLos Barnum; and Deloss Barnum.