Oscar Harger (January 12, 1843 – November 6, 1887) was an American invertebrate zoologist and paleontologist known for his studies on isopods, and for his work as an paleontological assistant to Othniel Charles Marsh.

He was obliged throughout his college course to maintain himself by teaching and mathematical work, and he perhaps injured his health permanently by the severe economy which he practiced at that time.

In his boyhood he had been an enthusiastic student of botany, and his success in this department of natural history led him on graduation to take up the study of zoology with Professor Verrill of the Sheffield Scientific School.

He had already shown his special aptitude for original work and had begun important investigations, when he accepted in 1870 the position of Assistant in Paleontology under Professor Marsh, which he retained until his death.

He is commemorated in the genus Hargeria, a fossil bird,[1] and the species Miacis hargeri, an extinct carnivorous mammal.