Eugen Woldemar Bostroem (13 October 1850 – 24 May 1928) was a Baltic German pathologist. He was born in Fellin (today known as Viljandi), in the Livonian Governorate of the Russian Empire (present-day Estonia).
He studied medicine at the universities of Leipzig and Erlangen, receiving his degree in 1876. Afterwards he was an assistant to Friedrich Albert von Zenker (1825–1898) at the pathology institute in Erlangen. From 1883 to 1926 he was a professor of general pathology and pathological anatomy in Gießen.
In 1890 Bostroem reportedly isolated the causative organism of actinomycosis from a culture of grain, grasses, and soil. After Bostroem's discovery there was a general misconception that actinomycosis was a mycosis that affected individuals who chewed grass or straw. The agents of actinomycosis are now known to be endogenous organisms of the mucous membranes, in most cases Actinomyces israelii, a species named after surgeon James Israel, who first discovered its presence in humans in the late 1870s.
In 1883 Bostroem was the first to describe a rare condition known as splenogonadal fusion. Since his discovery, approximately only 150 cases have been documented.