Hermanus Willem Koekkoek (Amsterdam, January 7, 1867 - there, September 9, 1929) was a Dutch painter, best known for his military scenes. He was part of the famous Koekkoek painters' family and was the son of city painter Willem Koekkoek and brother of Marinus Adrianus Koekkoek.

Hermanus Willem Koekkoek was educated by his father, Willem Koekkoek. He initially lived and worked in Amsterdam, stayed in London from 1887 to 1891, where his uncles Hermanus Koekkoek de Jonge and Barend Hendrik Koekkoek were in the art trade, then returned to Amsterdam and left for London again in 1901. In the early 1920s he returned to his hometown, where he died in 1929, aged 62.

Hermanus Willem Koekkoek made his name primarily as a painter with military scenes. He was one of the few Dutch painters who practiced this genre. Many of his works deal with military operations from the Franco-Prussian War (1870-1871), for which he conducted meticulous historical research. He preferred to paint cavalry charges, but daily soldier life also had his attention.

Several of his works can be seen in the Army Museum in Delft.

In addition to military scenes, Koekkoek also made portraits, genre works, historical scenes and animal scenes.